OpenSSH 9.7 released
OpenSSH plans to remove support for the DSA signature algorithm in early 2025 and compile-time disable it later this year.
DSA, as specified in the SSHv2 protocol, is inherently weak - being limited to a 160 bit private key and use of the SHA1 digest. Its estimated security level is only 80 bits symmetric equivalent.
OpenSSH has disabled DSA keys by default since 2015 but has retained run-time optional support for them. DSA was the only mandatory-to-implement algorithm in the SSHv2 RFCs[3], mostly because alternative algorithms were encumbered by patents when the SSHv2 protocol was specified.
This has not been the case for decades at this point and better algorithms are well supported by all actively-maintained SSH implementations. We do not consider the costs of maintaining DSA in OpenSSH to be justified and hope that removing it from OpenSSH can accelerate its wider deprecation in supporting cryptography libraries.
This release makes DSA support in OpenSSH compile-time optional, defaulting to on. We intend the next release to change the default to disable DSA at compile time. The first OpenSSH release of 2025 will remove DSA support entirely.