KCV Calculator
Compute Key Check Values for DES, TDES and AES keys: TDES encrypts a zero block, AES uses the X9.24-1:2017 CMAC method and the legacy AES-ECB method. Essential for key loading ceremonies and HSM validation.
Follows ANSI X9.24-1:2017 / TR-31:2018 key check valuesDES / TDES zero-block (3 bytes); AES-CMAC (5 bytes, KCV algorithm 01) and legacy AES-ECB (3 bytes)·verified Oct 2026· double-checked Oct 2026— CMAC per NIST SP 800-38B; 2,257 KCVs match Python cryptography and OpenSSL
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How KCV works
A Key Check Value is a short fingerprint of a cryptographic key used to verify that two parties hold the same key without revealing the key itself.
DES / TDES KCV: encrypt 8 zero bytes (0000000000000000) with DES or TDES in ECB mode and take the first 3 bytes. Double-length keys use EDE with K3 = K1. Parity bits do not change the result.
AES KCV (X9.24-1:2017, TR-31:2018): compute AES-CMAC (NIST SP 800-38B) over one block of 16 zero bytes and take the first 5 bytes.
Legacy AES KCV: encrypt 16 zero bytes with AES-ECB and take the first 3 bytes. Older HSMs and key forms still show this one, so check which method the other side uses.
Some systems show 2, 4 or more bytes of the same output: compare against the full block shown in step 3.