Deprecating the Use of SHA-1 in DNSSEC Signature Algorithms
updates
Extracted elements (11)
SHA-1's cryptographic security has been diminishing over time as various attacks have weakened its underpinnings; multiple stronger algorithms are now widely available, and some implementations have already removed SHA-1 support, making it no longer fully interoperable in DNSSEC.
Operators must take care when deploying software packages and operating systems that may have already removed SHA-1 support; manual builds may be needed to continue supporting required validation levels during the transition.
Support for validating SHA-1-based DNSSEC signatures has been removed from some systems, meaning SHA-1 as part of a DNSSEC signature algorithm is no longer fully interoperable. Implementations must continue to support validation for backward compatibility during the transition period.
If no other DS records of accepted cryptographic algorithms are available, the DNS records below the delegation point MUST be treated as insecure.
Operators of validating resolvers MUST treat DNSSEC signing algorithms RSASHA1 and RSASHA1-NSEC3-SHA1 as unsupported, rendering responses insecure if they cannot be validated by other supported signing algorithms.
The RSASHA1 and RSASHA1-NSEC3-SHA1 algorithms MUST NOT be used when creating DNSKEY and RRSIG records.
Validating resolver implementations MUST continue to support validation using RSASHA1 and RSASHA1-NSEC3-SHA1 algorithms, as they are diminishing in use but still actively used by some domains as of publication.
IANA updated the RSASHA1-NSEC3-SHA1 (number 7) entry in the 'DNS Security Algorithm Numbers' registry: 'Use for DNSSEC Signing' is MUST NOT; 'Implement for DNSSEC Signing' is NOT RECOMMENDED; 'Use for DNSSEC Validation' is RECOMMENDED; 'Implement for DNSSEC Validation' is MUST.
IANA updated the RSASHA1 (number 5) entry in the 'DNS Security Algorithm Numbers' registry: 'Use for DNSSEC Signing' is MUST NOT; 'Implement for DNSSEC Signing' is NOT RECOMMENDED; 'Use for DNSSEC Validation' is RECOMMENDED; 'Implement for DNSSEC Validation' is MUST.
IANA updated the SHA-1 (value 1) entry in the 'Digest Algorithms' registry: 'Use for DNSSEC Delegation' and 'Implement for DNSSEC Delegation' are set to MUST NOT; 'Use for DNSSEC Validation' is RECOMMENDED; 'Implement for DNSSEC Validation' is MUST.
RSASHA1 and RSASHA1-NSEC3-SHA1 are deprecated for DNSSEC delegation and signing because these algorithms are no longer considered to be secure, due to progressive weakening of SHA-1's cryptographic underpinnings.