The cryptographic algorithm and key size requirements included when DomainKeys Identified Mail (DKIM) was designed a decade ago are functionally obsolete and in need of immediate revision. This document updates DKIM requirements to those minimally suitable for operation with currently specified algorithms.
RFC 8301-2018 history
2018RFC 8301-2018 Cryptographic Algorithm and Key Usage Update to DomainKeys Identified Mail (DKIM)