Local Master Key Triple DES Variant scheme

Variants are applied to the Local Master Key in the HSM for encryption of double and triple length keys. These variants are calculated as follows:

1.        Select the appropriate LMK pair, for example:

0123 4567 89AB CDEF 3131 3131 3131 3131.

2.        Identify which Variant of the LMK is required and select the appropriate offset value:

Variant 2: A6.

3.        Exclusive-OR add the selected offset to the first byte of the second key within the LMK pair (31 in the example above).

4.        Replace the left-most byte of the LMK pair with the result of Step 3 and use the  resulting key as the specified Variant:

Variant 2 = 0123 4567 89AB CDEF 9731 3131 3131 3131.

The variants applied are as follows:

Double length key        Key 1 of 2 – A6

                                    Key 2 of 2 – 5A

Triple length key           Key 1 of 3 – 6A

                                    Key 2 of 3 – DE

                                    Key 3 of 3 – 2B

When the Variants are applied to the standard test LMK set, the first bytes of the second key are as follows: