Encrypt zeros DES-key verification algorithm

The cryptographic engine provides a method for verifying the value of a DES cryptographic key or key part without revealing information about the value of the key or key part.

In this method the single-length or double-length key DEA encodes a 64-bit value that is all zero bits. The leftmost 32 bits of the result are compared to the trial input value or returned from the Key Test and Key Test2 verbs.

For a single-length key, the key DEA encodes an 8-byte, all-zero-bits value.

For a double-length key, the key DEA triple-encodes an 8-byte, all-zero-bits value. The left half (high-order half) key encodes the zero-bit value, this result is DEA decoded by the right key half, and that result is DEA encoded by the left key half.