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4.1.6 Key Derivation

NIST PIV and digital identity SP 800-73-4
All changes in this version
first version loaded 4 Secure Messaging part of 4.1

Title

Key Derivation

Control

The session keys shall be derived in Steps C7 and H10 of the protocol using the key derivation function from [SP800-56A , Section 5.8.1], with the auxiliary function H being the hash function specified as the KDF hash in Table 14 , the length of the keying material to be derived ( len ) being 512 bits for CS2 and 1024 bits for CS7, and OtherInfo being constructed using the concatenation format as show below:

Cipher Suite ID OtherInfo

CS2 0x04 || 0x09 || 0x09 || 0x09 || 0x09 || 0x08 || ID sH || 0x01 || CB H || 0x10 || T 16 (Q eH ) || 0x08 || ID sICC || 0x10 || N ICC || 0x01 || CB ICC CS7 0x04 || 0x0D || 0x0D || 0x0D || 0x0D || 0x08 || ID sH || 0x01 || CB H || 0x10 || T 16 (Q eH ) || 0x08 || ID sICC || 0x18 || N ICC || 0x01 || CB ICC

For Q eH , the coordinates of the ephemeral public key are converted from field elements to byte strings as specified in [SP800-56A , Appendix C.2], Field-Element-to-Byte String Conversion, and concatenated (with x first) to form a single byte string. The first 16 bytes from this byte string are included in OtherInfo .