Card

How can users gain access to the SCADA application?
Objective to consolidate access to all information sources – i.e. to make access available to all users via a single interface
Are any RAS modems utilised within the SCADA environment?
Is the RAS call back feature utilised?
Is the mandatory RAS encryption feature used?
Are users allowed multiple attempts at authentication on the RAS?
Has the RAS auditing feature been enabled?
How is access between the business / corporate network and SCADA network controlled?
How is the administrator password controlled?
How is vendor access to the SCADA network controlled – i.e. password changes after contract has been completed?
Are SLA’s for outsourced support agreements reviewed on a periodic basis?
Are critical components of the SCADA Network supported by a UPS and are these batteries tested on a regular basis to ensure that they are reliable?
What capacity management and monitoring of critical SCADA network systems is performed (i.e. CPU utilisation and hard disk drive space)?
Are legal captions utilised during the login process to the SCADA application and associated infrastructure / devices?
Has an intrusion detection system (IDS) been deployed within the SCADA environment?
Has security been a focus within the development and deployment of the SCADA network?
Is there additional staff screenings performed when staff are hired to work within the SCADA environment (inclusive of vendors etc)?

Policies & Procedures

Is there a defined security strategy for the SCADA environment?
Who is responsible / accountable for security management within SCADA environment? Has the ownership of this responsibility been clearly defined and/or stated in any documentation?
Are there any periodic security reviews of the SCADA network performed?
What procedures are in place to handle the disposal of SCADA network media and devices? Additionally, is there a process in place for the disposal of confidential information / documentation?
Are there any policies or procedures covering the introduction of new devices to the SCADA environment?
What formal change control procedures exist for the SCADA environment?
Does a formal disaster recovery plan exist for the SCADA environment?
Does a formal business continuity plan exist for the SCADA environment?
Do physical and logical security standards differ significantly between SCADA sites?
Has a standard operating environment (SOE) minimum baseline standard been developed for systems being introduced into the SCADA environment?
What security logs are maintained for critical computer equipment and how often are the logs reviewed?
Who is responsible for the reviewing of security logs?
Has access to event logs been restricted?
Upon commencement of employment, are users provided with IT security information as part of the induction process? Additionally, are users provided with further information on security issues on a periodic basis?
What procedures exist to monitor dial-in access?
Is there a formally defined backup and recovery procedure?
Are encryption techniques and/or passwords applied to backup tapes?

Physical Access

How is physical access to SCADA terminals controlled?
Are SCADA control rooms segregated from other rooms?
What building security exists at remote sites to prevent unauthorised access?
What authentication methods are used at remote sites to allow access – i.e. swipe cards?
Are external windows at remotes sites barred?
What alarm systems have been employed at remote sites?

Network Security

Have all deployed routers been configured to ensure the filtering of communications that are unauthorised or not required?
What traffic control and monitoring capabilities have been deployed – i.e. all communication travels to a central point before traversing further on the network.
How are dial-in facilities to the SCADA environment secured?
How is suspicious or unusual activity on the SCADA WAN detected?
What firewall configurations have been set up to segregate the SCADA WAN from the United Water corporate network?
Are all key filtering devices on the network (such as routers and firewalls) configured to log all attempts to access the network? If so are they reviewed on a regular basis?
Have the auditing features of all routers and firewalls been enabled?
Has access to event logs been restricted?
How is the management of patches / hot fixes controlled in regards to firewalls and routers?
What backup and recovery measures are in place for network resources – firewalls and routers?
Has SNMP been implemented on core infrastructure?
Has any wireless equipment been deployed within the SCADA environment – has this been configured to a secure state?
Are all default passwords removed from SCADA devices after implementation?
Does a development environment exist to test changes prior to deployment into the SCADA network production environment?

Workstation Security

What operating systems (version) are installed on SCADA terminals?
Have operating system level passwords been activated on all SCADA terminals?
Do passwords have an indefinite expiry date?
What file and directory permission controls have been implemented on SCADA terminals to restrict unauthorised access by general users?
What logs are generated at the operating system level?
Has access to event logs been restricted?
What tools and services at the operating system level have been restricted for general users?
Who is responsible for patch management of SCADA terminals?
Has an audit feature been enabled for all SCADA terminals?
Are default services available with the operating system restricted?
Is virus protection implemented? Is this software manually or automatically updated?
Are shares enabled on SCADA terminals / workstations?
Are SCADA terminals backed up on a regular basis?
Is registry auditing of SCADA terminals performed?
Are user reviews and associated access rights performed on a regular basis?

SCADA Application Security

What are the username and password requirements of SCADA application?
Are session time out features activated?
Are complex passwords enforced to access the SCADA application?
Are user reviews and associated access rights performed on a regular basis?

System Penetration Testing

Internal penetration testing
External penetration testing
Password strength tests

Changes to the SCADA network

Please provide / list all potential changes being considered to the SCADA network.

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Trojan software has been found in ATMs located in Eastern Europe

by Derek on Jun.25, 2009, under Banking and EFTPoS

This is Great, I want one of these cards and a list of ATM’s.

http://www.sophos.com/blogs/gc/g/2009/03/18/details-diebold-atm-trojan-horse-case/

http://www.theregister.co.uk/2009/03/17/trojan_targets_diebold_atms/

From the Security Now Podcast http://www.grc.com/sn/sn-200.htm

Steve: It’s like, oh, goodness, yeah. It’s quite something. So the big news, though, I just sort of had to kind of smile because I told all of our listeners this was going to happen. I said just wait, this is a bad idea, we’re going to see how bad it is. Trojans have – Trojan software has been found in ATMs located in Eastern Europe.

Leo: Oh. Oh.

Steve: From many different vendors.

Leo: Oh, dear.

Steve: But what one thing do all of the trojan-infected ATMs have in common, Leo?

Leo: Let me guess.

Steve: Mm-hmm.

Leo: Windows?

Steve: Windows XP.

Leo: Ai yi yi.

Steve: The LSASS service is the manager of protected content in the system. It’s not quite the right acronym. I can’t think of what it is right now. But it’s like the main security service. And fake ones have been found in the Windows directory. The LSASS EXE normally lives in the Windows System32 directory. They were written in Borland’s Delphi.

Leo: You’re kidding.

Steve: No.

Leo: Well, that’s kind of sophisticated for a hacker. Wow.

Steve: And it’s considered, I mean, it’s commercial-grade code. It’s good code.

Leo: Oh, boy.

Steve: These are not remote installation Trojans. It’s believed that somebody had to have access to the machines.

Leo: Oh, even worse.

Steve: But they have special credit cards. When they swipe the special credit card in the infected machine, it accesses the trojan software, which among other things allows them to dump out all the cash from the machine. But in the meantime it’s logging all of the users’ information and PINs, which it’s able to dump out encrypted with DES encryption from the printer, from the ATM printer in the front of the machine.

Leo: Wow.

Steve: So the – and anyway, so it’s interesting to me. Again, it’s, you know, people defended the idea of implementing these things that I contend should never have been written in Windows. They say, well, but it’s easier to write them. And it’s like, yes.

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DUKPT Overview and Transaction notes

by Derek on Jun.22, 2009, under Banking and EFTPoS

Hi,

Recently I a questing was asked on another post relating to DUKPT. Given I have lots of material on the subject I thought I would create this thread. Link

I will come back at some stage and expand on this when I get time.

Transaction Process narrative:

The diagram describes a mobile terminal/ATM is described using the a AS2805 (‘2805′) message type and 3DES DUKPT and dual direction auth SSL from the terminal to the aquirer (transaction switch).

A good explanation of DUKPT can also be found at Wikipedia.

Diagram of the flow

DUKPT transaction flow - terminal to bank

Background notes:

The terminal or ATM firstly encrypts the user entered pin (may be a unique DUKPT key or static, depending on the design and banks involved) prior to incorporating it into the AS 2805 transaction message.
the message is then encrypted again using the DUKPT key which has been established through the merchant logon process within the aquirer Host Security Module (HSM) i.e. the user entered pin is encrypted separately and encapsulated within the DUKPT encrypted 2805 message to provide full message encryption.
In the diagram a separate dual authenticating SSL session is also used between the terminal/ATM and the aquirers infrastructure. This allowing the transaction including the pin to traverse the external Wired/GPRS/LAN within 2 primary independent layers of encryption, with a 3^rd protecting the PIN.
When the transaction enters the aquirer environment the message encapsulation layer provided by SSL is removed. This leaving the DUKPT’ed 2805 message which also encapsulates the separately encrypted PIN.
This encrypted message is passed to the aquirer switch engine through to the aquirer’s HSM for decryption of the 2805 message excluding the user entered pin.
This is when transactional information necessary for aquirer’s merchant reporting (truncated card number, transaction amount, transaction type, etc.) and fraud management data is collected.
The aquirer switch then passes the encrypted PIN to the aquirer HSM requesting that the PIN be decrypted using the aquirer’s PIN encryption and translated to the next banks (Bank 1) PIN Encryption Key (Pin translation only occurs within the aquirer HSM) This is then sent back to the aquirer Switch engine as the Bank 1 encrypted PIN.
The aquirer switch engine then send the decrypted 2805 message with the newly encrypted PIN back to aquirer HSM to be encrypted with the Bank 1 MAC key.
The resultant Bank 1 key encrypted message is then sent to Bank 1 for processing and/or passing to the card issuer (using a similar process as described above).
When the result is received back from the issuing bank it is encrypted with the Bank 1 MAC key (the pin will not be present in the result message).
This is then decrypted by the aquirer HSM, the transaction fate result stored into the aquirer merchant reporting system and the transaction fate re-encrypted with the original aquirer DUKPT key (should be different per terminal/merchant instance) and the result sent back to the terminal through the original established SSL encrypted terminal connection.

The aquirer may terminate the the SSL connection on a hardware device such as a CISCO Content Service Switch (CSS), or equivalent instead of the design described in the diagram which terminates onto a SSL session server/gateway (Possibly including a Certificate Authority) or on the aquirer transaction switch.

When PIN blocks are received by the aquirer processing centre, the PIN encryption is translated from the terminal key to the Local Master Key (LMK) by the Host Security Modules (HSM).

When the message is sent on the upstream bank interchange link to the issuer or gateway , the aquirer HSM translates the encrypted PIN block from the LMK to the Zone Master Key (ZMK) of the aquirer interchange link. The PIN block is always encrypted using DEA3 (3DES) whenever outside of the Terminal or ATM.

HSM-8000-User Guide V2.2

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EFT Syetms and Device Considerations

by Derek on Aug.05, 2008, under Banking and EFTPoS, Security

EFT devices and systems differ depending on hardware vendor, country and bank / payment aggregator.
Below is a list of things you may like to consider. This list is off the top of my head so it is probably not complete.

Looking at the products and relationships us usually a good start.

Things to consider:

Card skimming methods
Some EFT POS devices restrict the connection of a skimmer
Review levels of associated fraud
Review devices and EFT methods
Review terminal identification (merchant and customer)
Manual processing. (internal and external)
eCommerce products
PC based software
Dedicated server services (Nobil, etc.)
Web based engine (Custom objects, Web pop-ups, etc)
Authorisation / identification methods (Merchant and customer)
TCPIP session hijacking / session spoofing
Direct Debit as well as Credit Cards.
Swift (methods and controls)
Telegraphic transfer (methods and controls)
Payment aggregator relationships (eg. Payment Tech, manual processing, cheque scanning, etc.)
Internet banking facilities (attack / penetration, Certificate registration / management, ISP SLA’s, etc.)
Implementation of Smart Card and / or alternative customer recognition devices.
Outsourcing and associated risks / service level agreements
Payment processing
Payment clearance
Payment switching
Reporting (segregation of merchant / customers / aggregators / partners / local / international)
Fraud detection and reporting
3rd party acquiring risks
Single merchant ID many businesses
Allows moneys to be laundered if the payment aggregator does not place appropriate controls on the merchant.
Encryption used
Internet / trusted partner / inter-bank / extranet
Private and / or public certificates
Single use certificates
Client side certificates
Remittance advice processes and controls.
EFT disaster recovery and manual fall back procedures (associated security and reconciliation risks)
Trusted partner relationships, SLA’s, liabilities and risks.
EFT regulatory / legal requirements (inter-bank and government)
Refund processing / authorisation. (policies, procedures, controls, etc.)
CVV, CVV-2 / CVC-2 processing and management. (http://www.atlanticpayment.com/CVV.htm)
Fraud detection mechanism (neural networks, inter-bank / department customer checks, etc)
Supported card schemes (AMEX/Visa/Mastercard/Discover/etc )
Review EFT floor limits (corporate and SME merchants)
Review the ability to withhold merchant settlement until the presence of fraud has been determined.
Review customer identification details. Such as (This varies around the world depending on local regulations / privacy laws)
Review real-time and batched processing methods and controls (sequence numbers, access to raw data, etc.)
Review processing with and without expiry dates. (exception controls and policies)
Review exception / fraud reports.
Review payment store and forward policies and procedures.
Review Pre-Auth and Completion controls.
Token based payment (eCash, etc)
Merchant reconciliation, reporting methods and controls (paper, Internet, email, PDF, Fax, etc.) and associated security.
Real time gross settlement policies, procedures and controls. (IT and amounts)
Card issuing policies and procedures. (customer ID checks, etc)
Banking infrastructure (ingress / egress) controls and security. (Web, partner, payment switches, outsourced infrastructure, monitoring / reporting.)
Use of Internet technologies for inter-bank transfers and remote equipment.
Physical security and controls of devices, ATM,s, line encryptors, etc.

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Internet Banking Security Assessment Considerations

by Derek on Aug.05, 2008, under Banking and EFTPoS, Security

I was asked some time ago what sort of things may be considered when looking at Internet Banking.

Below is a list of things which could be considered. It was just a brain dump and as such may not be complete.

Don’t underestimate the value of standard for your infrastructure, website configuration, database engine configuration/architecture,staging environment and development/QA environments.

Some thoughts:

Many don’t lock accounts after X failed logins, this is normally done for good customer service, but leaves the system vulnerable.

- And all the other things expected for a remote login session (forced password changes, aging, etc))
- Tools such as Brutus may be use to brute force hack authenticated sessions.

Many allow session sequence numbers to be incremented, allowing an authenticated user to view other customer session.

- These may be server side, client side, cookie based, etc.
- Get someone to check the development methodologies and the code being used.
- Database query strings can be placed into test entry fields, allowing table dumps to browser.
- Check all pages served are secure and contain user authentication flags.

Customer data may not be segregated, this needs to be checked.
Customer data should not reside on the Web Server.

Authentication databases / system data should not reside on the webserver.
The databases should reside on a private/semi-private network.

- A different segment to the main banking system.

Webserver should be dual homed or equivalent (some VLAN techniques are good)

- Separate private and public network cards, monitoring/backup/administration
- Infrastructure set-up to explicitly deny inbound/outbound ports, private IP & monitoring escaping from the network.

At all data segregation points ensure rules are in place which appreciates the traffic though that point.

All customer data where possible should be sourced from a secure back-end database.

- This may be a staging environment. i.e. no the main banking system.
- This usually allows for transactions to appear real time to the customer.
- Many transactions may be batched in reality. (internal or external to the bank)

Ensure suitable rules have been set-up on firewalls.

- There should be inbound and outbound rules on firewalls and filtering routers.

Don’t allow any infrastructure on the front end to allow remote administrative connections. (telnet, etc.)

- Use the serial console port to connect to a server or back-end terminal server.

Look for the segregation / staging of online customer content from main banking systems

Ensure that a separate development / QA / production environment system and suitable process is in place.

Services not used by the system are active

- These should be disabled.

Port scan of the supporting infrastructure (routers /switches) and server(s).

- Investigate the reasons for all open ports.

Don’t use the main gateway for trusted partner access (clearing / RAS / etc.)
Do all that standard IIS checks and NT checks (Sample scripts, change management, patching methodologies, etc.)
Ensure denial of service precaution have been taken into account for all infrastructure and server equipment.
Check the adequacy of the escalation procedures used.

- Look for real-time monitoring and alerting.
- Look for responsibility matrix.
- Look for ownership of issues.

Consider upstream carrier(s) vulnerability (denial of service, IP spoofing, DNS hacking, etc)
Consider social engineering of customer, administrative, partner accounts / systems / infrastructure.

- Helpdesk procedures and policies and/or alternate technologies (Caller ID, Gateway IP, etc.).

Use dynamic passwords where possible (SecureID, TACACS, etc.).
Use encrypted tunnelling where needed (IPSec, Firewall 1, etc)
Consider looking at other customer authentication methods to enhance existing methods.

- Digital cert, IP address locked to account, etc.
- Consider use of CVV or CVN for bank issued cards.

Consider how passwords are distributed /changed for customers.

- Plain text email, telephone, etc.
- Can passwords be changed online?

Is additional authentication used between sections of the services once authenticated?
Consider what the customer has access to once authenticated.

- Look at SWIFT, RTGS, inter-bank transfers, access to credit cards, etc.
- If an attacker does get in, what can the do?

Use techniques to ensure pages, customer details are not cached at ISP, or client system.

- These are flags that can be set within pages.
- Normally SSL is cached, but some proxy vendors have been playing with techniques to do so.
- Caching of SSL pages on the client system can be turned on on some browsers.
- May banks use a Java (or similar) applet for all customer interaction, restricting all caching issues.

Ensure paper based and on-line liability clauses are available are address all effected areas.
Ensure within the customer sign-up process banking liability is reduced.

- I’ve seen statements like “use this system at your own risk, responsibility for any liability or claim will NOT……”
- Not very customer focused, but that’s what their legal department recommended.

All of the above can effect the security and/or operation of an on-line banking system.

Other things to consider:

External development and support of the application.
Ownership and management of the hardware/applications
Publishing points for new content (internal/private/trusted network or Internet)
Topology of front end. i.e. Security Architecture document should be in place and managed appropriately.
Are limited AP tests performed whenever changes are made to the environment? i.e. integrated AP into Change management process.
Database access. Is it buffered or is it live to the core banking systems.
What facilities are provided? Direct debit + Credit Card + SWIFT + ……. Consider different scenarios for your attack depending on the feature.
What other services are shared within the network segment that the Internet Banking service is running. Can this be used to compromise the Internet Banking site. eg. different support/business/development organisations with differing security strategies/profiles.
Consider all external supporting services within you AP. Look at internal/external DNS poisoning opportunities, mail relay, etc. What IPS’s do they use has the ISP any opportunity to access systems or supporting services which may affect Internet Banking.
Depending on the size of the Bank, many organisation do not use the same support groups for infrastructure and the application. As a result external connections to the infrastructure may be provided for an external support organisation to administer the infrastructure.
Look at the business and user authentication methods and paths (client side certs, secure ID, SMART Card, etc). Consider two factor authentication and modern user identification methods. eg. what is your favourite food in addition to normal usernames and passwords. Do system administration staff use dynamic passwords (secureID, etc)?
See if the Internet Banking application sends email to users which may contain interesting information.
Better access to the application can generally be gained after access to the system. i.e. get an legitimate account on the system. I have found that some sample/administration screens have been restricted to authenticated users only.
Consider social engineering the Help desk to have an account password reset.

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Mobile Banking Security and Risk Assessment Considerations

by Derek on Aug.05, 2008, under Banking and EFTPoS, Security

When considering Mobile Banking security and the associated risk, the an assessment approach depends greatly on the solution being created or provided.
Generally the approach is based on layered standards supporting and surrounding the technologies and techniques used.

Here are some things to consider.

Security assessments generally focuses on two main things.

1/ Sensitivity of the data
What is being sent. eg. Pin, credit card numbers, account balance, home address, bank account number, etc.
Data may not be sensitive to the bank, but may be considered by the client as sensitive.
etc……….

2/ Opportunity to access the data.
What medium is being used?
Is it easy to hack?
What encryption is being used?
Are all data paths secure (client and back end)?
Is there a 3rd party involved in the switching of the transactions?
etc………

Things to consider:

Pin resets sent via SMS to client, should not be used as the only method of accessing accounts. An additional client specific (possibly static) pass word/phrase should be used in addition to a dynamically generated pin. SMS can be sniffed (depending on mode and location).
If WAP is used, are all devices capable of encryption? If devices are not capable of encryption, do we deny access to these devices? If client side JAVA or intelligent device (win CE, etc), ensure this can not be compromised by a Trojan’s and other key logging techniques.
Has the organisation considered client side certificates to verify the device prior to transactions being accepted? Consider multiple device and user identification methods (very solution dependant).
Most mobile POS terminals encrypt the client entered Pin number, but do not encrypt everything within the transaction. If the transmission medium is compromised, we should consider if the encryption can be cracked and if unencrypted data is sensitive. Consider additional data encryption encapsulation i.e. use of all of message encryption (SSL, IPSEC) or use a terminal that utilises Derived Unique Key Per Transaction (DUKPT).
Many banking applications have been affected by typical hacks such as session hijacking, SQL injection, non random session keys (client side and server side), etc… These typical hacks should be considered in your Secure SDLC and QA Processes once you are aware of the technology used and/or deployed.
PBX systems and cabling distribution frames can have devices connected to collect transactions. Wireless devices are now being connected to these systems. The attacker sits in their car in the car park outside. This is often done in super markets.
Wireless transaction gateways if not encrypted are easily collected by anyone within wireless range. 802.11 and other wireless/infra-red mediums are being used (assess the technology and medium being used).
Has the organisation considered dynamic keys for mobile users? There are some very low cost SecureID type solutions available today, but customers need to have these devices on them when they want to do a transaction.

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Breaking VISA PIN

by Derek on Jul.02, 2008, under Banking and EFTPoS

Below is an article I found recently. This one of the most comprehensive descriptions of PIN Verification Value (PVV) hacking.

I thought I would replicate it here for my local reference.

As comments have been made regarding the grammar used in the original text, I have corrected some of the obvious errors whilst maintaining the context of the original material.

http://69.46.26.132/~biggold1/fastget2you/tutorial.php

——– Original Text ———-

Foreword
Have you ever wonder what would happen if you lose your credit or debit card and someone finds it. Would this person be able to withdraw cash from an ATM guessing, somehow, your PIN? Moreover, if you were who finds someone’s card would you try to guess the PIN and take the chance to get some easy money? Of course the answer to both questions should be “no”. This work does not deal with the second question, it is a matter of personal ethics. Herewith I try to answer the first question.

All the information used for this work is public and can be freely found in Internet. The rest is a matter of mathematics and programming, thus we can learn something and have some fun. I reveal no secrets. Furthermore, the aim (and final conclusion) of this work is to demonstrate that PIN algorithms are still strong enough to provide sufficient security. We all know technology is not the weak point.

This work analyses one of the most common PIN algorithms, VISA PVV, used by many ATM cards (credit and debit cards) and tries to find out how resistant is to PIN guessing attacks. By “guessing” I do not mean choosing a random PIN and trying it in an ATM. It is well known that generally we are given three consecutive trials to enter the right PIN, if we fail ATM keeps the card. As VISA PIN is four digit long it’s easy to deduce that the chance for a random PIN guessing is 3/10000 = 0.0003, it seems low enough to be safe; it means you need to lose your card more than three thousand times (or losing more than three thousand cards at the same time :) until there is a reasonable chance of losing money.

What I really meant by “guessing” was breaking the PIN algorithm so that given any card you can immediately know the associated PIN. Therefore this document studies that possibility, analyzing the algorithm and proposing a method for the attack. Finally we give a tool which implements the attack and present results about the estimated chance to break the system. Note that as long as other banking security related algorithms (other PIN formats such as IBM PIN or card validation signatures such as CVV or CVC) are similar to VISA PIN, the same analysis can be done yielding nearly the same results and conclusions.

VISA PVV algorithm

One of the most common PIN algorithms is the VISA PIN Verification Value (PVV). The customer is given a PIN and a magnetic stripe card. Encoded in the magnetic stripe is a four digit number, called PVV. This number is a cryptographic signature of the PIN and other data related to the card. When a user enters his/her PIN the ATM reads the magnetic stripe, encrypts and sends all this information to a central computer. There a trial PVV is computed using the customer entered PIN and the card information with a cryptographic algorithm. The trial PVV is compared with the PVV stored in the card, if they match the central computer returns to the ATM authorization for the transaction. See in more detail.

The description of the PVV algorithm can be found in two documents linked in the previous page. In summary it consists in the encryption of a 8 byte (64 bit) string of data, called Transformed Security Parameter (TSP), with DES algorithm (DEA) in Electronic Code Book mode (ECB) using a secret 64 bit key. The PVV is derived from the output of the encryption process, which is a 8 byte string. The four digits of the PVV (from left to right) correspond to the first four decimal digits (from left to right) of the output from DES when considered as a 16 hexadecimal character (16 x 4 bit = 64 bit) string. If there are no four decimal digits among the 16 hexadecimal characters then the PVV is completed taken (from left to right) non decimal characters and decimalizing them by using the conversion A->0, B->1, C->2, D->3, E->4, F->5. Here is an example:

Output from DES: 0FAB9CDEFFE7DCBA

PVV: 0975

The strategy of avoiding decimalization by skipping characters until four decimal digits are found (which happens to be nearly all the times as we will see below) is very clever because it avoids an important bias in the distribution of digits which has been proven to be fatal for other systems, although the impact on this system would be much lower. See also a related problem not applying to VISA PVV.

The TSP, seen as a 16 hexadecimal character (64 bit) string, is formed (from left to right) with the 11 rightmost digits of the PAN (card number) excluding the last digit (check digit), one digit from 1 to 6 which selects the secret encrypting key and finally the four digits of the PIN. Here is an example:

PAN: 1234 5678 9012 3445
Key selector: 1
PIN: 2468

TSP: 5678901234412468

Obviously the problem of breaking VISA PIN consists in finding the secret encrypting key for DES. The method for that is to do a brute force search of the key space. Note that this is not the only method, one could try to find a weakness in DEA, many tried, but this old standard is still in wide use (now been replaced by AES and RSA, though). This demonstrates it is robust enough so that brute force is the only viable method (there are some better attacks but not practical in our case, for a summary see LASEC memo and for the dirty details see Biham & Shamir 1990, Biham & Shamir 1991, Matsui 1993, Biham & Biryukov 1994 and Heys 2001).

The key selector digit was very likely introduced to cover the possibility of a key compromise. In that case they just have to issue new cards using another key selector. Older cards can be substituted with new ones or simply the ATM can transparently write a new PVV (corresponding to the new key and keeping the same PIN) next time the customer uses his/her card. For the shake of security all users should be asked to change their PINs, however it would be embarrassing for the bank to explain the reason, so very likely they would not make such request.

Preparing the attack

A brute force attack consists in encrypting a TSP with known PVV using all possible encrypting keys and compare each obtained PVV with the known PVV. When a match is found we have a candidate key. But how many keys we have to try? As we said above the key is 64 bit long, this would mean we have to try 2^64 keys. However this is not true. Actually only 56 bits are effective in DES keys because one bit (the least significant) out of each octet was historically reserved as a checksum for the others; in practice those 8 bits (one for each of the 8 octets) are ignored.

Therefore the DES key space consists of 2^56 keys. If we try all these keys will we find one and only one match, corresponding to the bank secret key? Certainly not. We will obtain many matching keys. This is because the PVV is only a small part (one fourth) of the DES output. Furthermore the PVV is degenerated because some of the digits (those between 0 and 5 after the last, seen from left to right, digit between 6 and 9) may come from a decimal digit or from a decimalized hexadecimal digit of the DES output. Thus many keys will produce a DES output which yields to the same matching PVV.

Then what can we do to find the real key among those other false positive keys? Simply we have to encrypt a second different TSP, also with known PVV, but using only the candidate keys which gave a positive matching with the first TSP-PVV pair. However there is no guarantee we won’t get again many false positives along with the true key. If so, we will need a third TSP-PVV pair, repeat the process and so on.

Before we start our attack we have to know how many TSP-PVV pairs we will need. For that we have to calculate the probability for a random DES output to yield a matching PVV just by chance. There are several ways to calculate this number and here I will use a simple approach easy to understand but which requires some background in mathematics of probability.

A probability can always be seen as the ratio of favorable cases to possible cases. In our problem the number of possible cases is given by the permutation of 16 elements (the 0 to F hexadecimal digits) in a group of 16 of them (the 16 hexadecimal digits of the DES output). This is given by 16^16 ~ 1.8 * 10^19 which of course coincides with 2^64 (different numbers of 64 bits). This set of numbers can be separated into five categories:

Those with at least four decimal digits (0 to 9) among the 16 hexadecimal digits (0 to F) of the DES output.

Those with exactly only three decimal digits.

Those with exactly only two decimal digits.

Those with exactly only one decimal digit.

Those with no decimal digits (all between A and F).

Let’s calculate how many numbers fall in each category. If we label the 16 hexadecimal digits of the DES output as X1 to X16 then we can label the first four decimal digits of any given number of the first category as Xi, Xj, Xk and Xl. The number of different combinations with this profile is given by the product 6 i-1 * 10 * 6j-i-1 * 10 * 6k-j-1 * 10 * 6 l-k-1 * 10 * 1616-l where the 6’s come from the number of possibilities for an A to F digit, the 10’s come from the possibilities for a 0 to 9 digit, and the 16 comes from the possibilities for a 0 to F digit. Now the total numbers in the first category is simply given by the summation of this product over i, j, k, l from 1 to 16 but with i < j < k < l. If you do some math work you will see this equals to the product of 104/6 with the summation over i from 4 to 16 of (i-1) * (i-2) * (i-3) * 6i-4 * 16 16-i ~ 1.8 * 1019.

Analogously the number of cases in the second category is given by the summation over i, j, k from 1 to 16 with i < j < k of the product 6i-1 * 10 * 6j-i-1 * 10 * 6k-j-1 * 10 * 616-k which you can work it out to be 16!/(3! * (16-13)!) * 103 * 6 13 = 16 * 15 * 14/(3 * 2) * 103 * 613 = 56 * 104 * 613 ~ 7.3 * 1015. Similarly for the third category we have the summation over i, j from 1 to 16 with i < j of 6 i-1 * 10 * 6j-i-1 * 10 * 616-j which equals to 16!/(2! * (16-14)!) * 102 * 614 = 2 * 103 * 615 ~ 9.4 * 1014. Again, for the fourth category we have the summation over i from 1 to 16 of 6i-1 * 10 * 616-i = 160 * 615 ~ 7.5 * 1013. And finally the amount of cases in the fifth category is given by the permutation of six elements (A to F digits) in a group of 16, that is, 616 ~ 2.8 * 1012.

I hope you followed the calculations up to this point, the hard part is done. Now as a proof that everything is right you can sum the number of cases in the 5 categories and see it equals the total number of possible cases we calculated before. Do the operations using 64 bit numbers or rounding (for floats) or overflow (for integers) errors won’t let you get the exact result.

Up to now we have calculated the number of possible cases in each of the five categories, but we are interested in obtaining the number of favorable cases instead. It is very easy to derive the latter from the former as this is just fixing the combination of the four decimal digits (or the required hexadecimal digits if there are no four decimal digits) of the PVV instead of letting them free. In practice this means turning the 10’s in the formula above into 1’s and the required amount of 6’s into 1’s if there are no four decimal digits. That is, we have to divide the first result by 104, the second one by 103 * 6, the third one by 102 * 62 , the fourth one by 10 * 63 and the fifth one by 64 . Then the number of favorable cases in the five categories are approximately 1.8 * 1015, 1.2 * 1012, 2.6 * 1011 , 3.5 * 1010, 2.2 * 109 respectively.

Now we are able to obtain what is the probability for a DES output to match a PVV by chance. We just have to add the five numbers of favorable cases and divide it by the total number of possible cases. Doing this we obtain that the probability is very approximately 0.0001 or one out of ten thousand. Is it strange this well rounded result? Not at all, just have a look at the numbers we calculated above. The first category dominates by several orders of magnitude the number of favorable and possible cases. This is rather intuitive as it seems clear that it is very unlikely not having four decimal digits (10 chances out of 16 per digit) among 16 hexadecimal digits. We saw previously that the relationship between the number of possible and favorable cases in the first category was a division by 10^4, that’s where our result p = 0.0001 comes from.

Our aim for all these calculations was to find out how many TSP-PVV pairs we need to carry a successful brute force attack. Now we are able to calculate the expected number of false positives in a first search: it will be the number of trials times the probability for a single random false positive, i.e. t * p where t = 2^56, the size of the key space. This amounts to approximately 7.2 * 10^12, a rather big number. The expected number of false positives in the second search (restricted to the positive keys found in the first search) will be (t * p) * p, for a third search will be ((t * p) * p) * p and so on. Thus for n searches the expected number of false positives will be t * p^n.

We can obtain the number of searches required to expect just one false positive by expressing the equation t * p^n = 1 and solving for n. So n equals to the logarithm in base p of 1/t, which by properties of logarithms it yields n = log(1/t)/log(p) ~ 4.2. Since we cannot do a fractional search it is convenient to round up this number. Therefore what is the expected number of false positives if we perform five searches? It is t * p^5 ~ 0.0007 or approximately 1 out of 1400. Thus using five TSP-PVV pairs is safe to obtain the true secret key with no false positives.

The attack

Once we know we need five TSP-PVV pairs, how do we get them? Of course we need at least one card with known PIN, and due to the nature of the PVV algorithm, that’s the only thing we need. With other PIN systems, such as IBM, we would need five cards, however this is not necessary with VISA PVV algorithm. We just have to read the magnetic stripe and then change the PIN four times but reading the card after each change.

It is necessary to read the magnetic stripe of the card to get the PVV and the encrypting key selector. You can buy a commercial magnetic stripe reader or make one yourself following the instructions you can find in the previous page and links therein. Once you have a reader see this description of standard magnetic tracks to find out how to get the PVV from the data read. In that document the PVV field in tracks 1 and 2 is said to be five character long, but actually the true PVV consists of the last four digits. The first of the five digits is the key selector. I have only seen cards with a value of 1 in this digit, which is consistent with the standard and with the secret key never being compromised (and therefore they did not need to move to another key changing the selector).

I did a simple C program, getpvvkey.c, to perform the attack. It consists of a loop to try all possible keys to encrypt the first TSP, if the derived PVV matches the true PVV a new TSP is tried, and so on until there is a mismatch, in which case the key is discarded and a new one is tried, or the five derived PVVs match the corresponding true PVVs, in which case we can assume we got the bank secret key, however the loop goes on until it exhausts the key space. This is done to assure we find the true key because there is a chance (although very low) the first key found is a false positive.

It is expected the program would take a very long time to finish and to minimize the risks of a power cut, computer hang out, etc. it does checkpoints into the file getpvvkey.dat from time to time (the exact time depends on the speed of the computer, it’s around one hour for the fastest computers now in use). For the same reason if a positive key is found it is written on the file getpvvkey.key. The program only displays one message at the beginning, the starting position taken from the checkpoint file if any, after that nothing more is displayed.

The DES algorithm is a key point in the program, it is therefore very important to optimize its speed. I tested several implementations: libdes, SSLeay, openssl, cryptlib, nss, libgcrypt, catacomb, libtomcrypt, cryptopp, ufc-crypt. The DES functions of the first four are based on the same code by Eric Young and is the one which performed best (includes optimized C and x86 assembler code). Thus I chose libdes which was the original implementation and condensed all relevant code in the files encrypt.c (C version) and x86encrypt.s (x86 assembler version). The code is slightly modified to achieve some enhancements in a brute force attack: the initial permutation is a fixed common steep in each TSP encryption and therefore can be made just one time at the beginning. Another improvement is that I wrote a completely new setkey function (I called it nextkey) which is optimum for a brute force loop.

To get the program working you just have to type in the corresponding place five TSPs and their PVVs and then compile it. I have tested it only in UNIX platforms, using the makefile Makegetpvvkey to compile (use the command “make -f Makegetpvvkey”). It may compile on other systems but you may need to fix some things. Be sure that the definition of the type long64 corresponds to a 64 bit integer. In principle there is no dependence on the endianness of the processor. I have successfully compiled and run it on Pentium-Linux, Alpha-Tru64, Mips-Irix and Sparc-Solaris. If you do not have and do not want to install Linux (you don’t know what you are missing ;-) you still have the choice to run Linux on CD and use my program, see my page running Linux without installing it.

Once you have found the secret bank key if you want to find the PIN of an arbitrary card you just have to write a similar program (sorry I have not written it, I’m too lazy :) that would try all 10^4 PINs by generating the corresponding TSP, encrypting it with the (no longer) secret key, deriving the PVV and comparing it with the PVV in the magnetic stripe of the card. You will get one match for the true PIN. Only one match? Remember what we saw above, we have a chance of 0.0001 that a random encryption matches the PVV. We are trying 10000 PINs (and therefore TSPs) thus we expect 10000 * 0.0001 = 1 false positive on average.

This is a very interesting result, it means that, on average, each card has two valid PINs: the customer PIN and the expected false positive. I call it “false” but note that as long as it generates the true PVV it is a PIN as valid as the customer’s one. Furthermore, there is no way to know which is which, even for the ATM; only customer knows. Even if the false positive were not valid as PIN, you still have three trials at the ATM anyway, enough on average. Therefore the probability we calculated at the beginning of this document about random guessing of the PIN has to be corrected. Actually it is twice that value, i.e., it is 0.0006 or one out of more than 1600, still safely low.

Results

It is important to optimize the compilation of the program and to run it in the fastest possible processor due to the long expected run time. I found that the compiler optimization flag -O gets the better performance, thought some improvement is achieved adding the -fomit-frame-pointer flag on Pentium-Linux, the -spike flag on Alpha-Tru64, the -IPA flag on Mips-Irix and the -fast flag on Sparc-Solaris. Special flags (-DDES_PTR -DDES_RISC1 -DDES_RISC2 -DDES_UNROLL -DASM) for the DES code have generally benefits as well. All these flags have already been tested and I chose the best combination for each processor (see makefile) but you can try to fine tune other flags.

According to my tests the best performance is achieved with the AMD Athlon 1600 MHz processor, exceeding 3.4 million keys per second. Interestingly it gets better results than Intel Pentium IV 1800 MHz and 2000 MHz (see figures below, click on them to enlarge). I believe this is due to some I/O saturation, surely cache or memory access, that the AMD processor (which has half the cache of the Pentium) or the motherboard in which it is running, manages to avoid. In the first figure below you can see that the DES breaking speed of all processors has more or less a linear relationship with the processor speed, except for the two Intel Pentium I mentioned before. This is logical, it means that for a double processor speed you’ll get double breaking speed, but watch out for saturation effects, in this case it is better the AMD Athlon 1600 MHz, which will be even cheaper than the Intel Pentium 1800 MHz or 2000 MHz.

In the second figure we can see in more detail what we would call intrinsic DES break power of the processor. I get this value simply dividing the break speed by the processor speed, that is, we get the number of DES keys tried per second and per MHz. This is a measure of the performance of the processor type independently of its speed. The results show that the best processor for this task is the AMD Athlon, then comes the Alpha and very close after it is the Intel Pentium (except for the higher speed ones which perform very poor due to the saturation effect). Next is the Mips processor and in the last place is the Sparc. Some Alpha and Mips processors are located at bottom of scale because they are early releases not including enhancements of late versions. Note that I included the performance of x86 processors for C and assembler code as there is a big difference. It seems that gcc is not a good generator of optimized machine code, but of course we don’t know whether a manual optimization of assembler code for the other processors (Alpha, Mips, Sparc) would boost their results compared to the native C compilers (I did not use gcc for these other platforms) as it happens with the x86 processor.

Update

Here is an article where these techniques may have been used.

http://redtape.msnbc.com/2008/08/could-a-hacker.html

3 Comments :access, algorithm, atm cards, attack, bank, Banking, bar, Card, conclusion, Credit, CVV, data, Debit, debit card, debit cards, DES, difference, easy money, EFT, Electronic, encryption, hack, Hacking, Internet, ISP, logarithm, magnetic stripe, Mall, Material, mathematics, money, permutation, personal ethics, php, Pin, probability, PVV, Reader, RSA, script, security, Shiraz, something, technique, technology, text, transaction, TSP-PVV, type, Verification, VISA, weak point more...

Financial Transaction Processing

by Derek on Jul.02, 2008, under Banking and EFTPoS

I have been recently working inside one of the larger Banks in Australia.
Through this work I have been looking at the controls and mechanisms surrounding the processing of credit and debit cards around the Asia Pacific.

I get perform many security architecture and payment systems assessments.
Over the years I have always considered the protection of the card data as one of the key considerations.

Until yesterday I had never seen an CVV or PVV decryption tools. I think some scripted use of these tools could be very interesting.
The site hziggurat29.com

Many of the other tools on this site are also very unique and worth a look.
Big thanks to ziggurat29 for providing such awesome tools.

As many of these sites are of this nature are difficult to find and often seem to vanish over the years, I have chosen to replicate the the text from this page and provide local copies on the files.
It is worth periodically visiting the ziggurat29 site every now and again to see if any additional tools have been posted.

One of the more extraordinary files is the Atalla Hardware Security Module (HSM) and BogoAtalla for Linksys emulation (simulation) tools. So I wonder if Eracom and Thales are shaking in their boots. Some how I don’t think so. ;-)

——– ziggurat29 Text ———

These are all Windows command-line utilities (except where noted); execute with the -help option
to determine usage.

DUKPT Decrypt (<- the actual file to download)

This is a utility that will decrypt Encrypted PIN Blocks that have been produced via the DUKPT triple-DES method. I used this for testing the output of some PIN Pad software I had created, but is also handy for other debugging purposes.

VISA PVV Calculator (<- the actual
file to download)

This is a utility that will compute and verify PIN Verification Values that have been produced using the VISA PVV technique. It has a bunch of auxiliary functions, such as verifying and fixing a PAN (Luhn computations), creating and encrypting PIN blocks, decrypting and extracting PINs from encrypted PIN blocks, etc.

VISA CVV Calculator (<- the actual file to download)

This is a utility that will compute Card Verification Values that have been produced using the VISA CVV technique. MasterCard CVC uses the CVV algorithm, so it will work for that as well. It will compute CVV, CVV2, CVV3, iCVV, CAVV, since these are just variations on service code and the
format of the expiration date. Verification is simply comparing the computed value with what you have received, so there is no explicit verification function.

Atalla AKB Calculator (<- the actual file to download)

This is a utility that will both generate and decrypt Atalla AKB cryptograms. You will need the plaintext MFK to perform these operations. When decrypting, the MAC will also be checked and the results shown.

BogoAtalla (<- the actual file to
download)

This is an Atalla emulator (or simulator). This software emulation (simulation) of the well-known Atalla Hardware Security Module (HSM) that is used by banks and processors for cryptographic operations, such as verifying/translating PIN blocks, authorising transactions by verifying
CVV/CSC numbers, and performing key exchange procedures, was produced for testing purposes. This implementation is not of the complete HP Atalla command set, but rather the just
portions that I myself needed. That being said, it is complete enough if you are performing acquiring and/or issuing processing functions, and are using more modern schemes such as Visa PVV and DUKPT, and need to do generation, verification, and translation.

This runs as a listening socket server and handles the native Atalla command set. I have taken some liberties with the error return values and have not striven for high-fidelity there (i.e., you may get a different error response from native hardware), but definitely should get identical positive
responses. Some features implemented here would normally require purchasing premium commands, but all commands here implemented are available. Examples are generating PVV values and encrypting/decrypting plaintext PIN values.

BogoAtalla for Linksys (<- the actual file to download)

This is the Atalla emulator ported to Linux and build for installation on an OpenWRT system. Makes for a really cheap ($60 USD) development/test device.

Local Files

bogoatalla002
atallaakbcalc
bogoatalla_10-1_mipsel
dukptdecrypt
visacvvcalc
visapvvcalc

22 Comments :algorithm, architecture, Australia, bank, BogoAtalla, Card, card verification, computations, Credit, CVV, data, Debit, debit card, debit cards, decrypt, decryption, decryption tools, DES, development, DUKPT, EFT, emulation, emulator, Eracom, financial transaction, hardware, hardware security, HSM, Linksys, Mall, mechanisms, payment, Pin, pin pad, processing, Protection, PVV, SAP, script, security, security architecture, server, Shiraz, simulation tools, SLA, SMS, technique, text, Thales, transaction, triple des, utility, Verification, VISA more...

“Contactless” credit cards with RFID are easily hacked

by Derek on Jun.18, 2008, under RFID

A blog posting on BoingBoing provides further discussion as to the
inappropriate deployment and of RFID chips within the existing payment
marketplace.

http://www.boingboing.net/2006/10/23/report_contactless_c.html

The underlying point of this article is, the card schemes and banks said they are using key rotating encryption of all data between the card and the acquirer/issuer, but this is clearly not the case in many situations.

Another interesting paper is ‘RFID Payment Card Vulnerabilities Technical Report’ located at:

http://www.nytimes.com/packages/pdf/business/20061023_CARD/techreport.pdf

Leave a Comment :acquirer, bank, BoingBoing, Card, card schemes, Chip, contactless credit cards, Credit, data, DES, encryption, hack, JAVA, javascript, payment, RFID, rfid chip, rfid chips, script, Shiraz, Technical, Vulnerabilities more...

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