Command Section
ISC-HMAC-FIXUP(8)                    BIND9                   ISC-HMAC-FIXUP(8)

       isc-hmac-fixup - fixes HMAC keys generated by older versions of BIND

       isc-hmac-fixup {algorithm} {secret}

       Versions of BIND 9 up to and including BIND 9.6 had a bug causing
       HMAC-SHA* TSIG keys which were longer than the digest length of the
       hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
       longer than 256 bits, etc) to be used incorrectly, generating a message
       authentication code that was incompatible with other DNS

       This bug has been fixed in BIND 9.7. However, the fix may cause
       incompatibility between older and newer versions of BIND, when using
       long keys.  isc-hmac-fixup modifies those keys to restore

       To modify a key, run isc-hmac-fixup and specify the key's algorithm and
       secret on the command line. If the secret is longer than the digest
       length of the algorithm (64 bytes for SHA1 through SHA256, or 128 bytes
       for SHA384 and SHA512), then a new secret will be generated consisting
       of a hash digest of the old secret. (If the secret did not require
       conversion, then it will be printed without modification.)

       Secrets that have been converted by isc-hmac-fixup are shortened, but
       as this is how the HMAC protocol works in operation anyway, it does not
       affect security. RFC 2104 notes, "Keys longer than [the digest length]
       are acceptable but the extra length would not significantly increase
       the function strength."

       BIND 9 Administrator Reference Manual, RFC 2104.

       Internet Systems Consortium, Inc.

       Copyright (C) 2010, 2013-2016 Internet Systems Consortium, Inc. ("ISC")

ISC                               2013-04-28                 ISC-HMAC-FIXUP(8)
Command Section