GitHub now requires 3072-bit RSA keys for new SSH uploads
From today, shorter RSA keys are rejected on upload, and GitHub switches on a post-quantum key exchange algorithm ahead of retiring SHA-1 SSH signatures entirely.
GitHub’s new RSA key size requirement takes effect today, 14 October. Any RSA SSH key uploaded from now on must be at least 3072 bits, for both signing and authentication; shorter keys, including the 2048-bit default that older versions of ssh-keygen still produce, are rejected.
GitHub has also switched on mlkem768x25519-sha256, a post-quantum key exchange algorithm, for SSH connections to github.com and GitHub Enterprise Cloud with Data Residency, though not yet in the US region. It’s a precursor to retiring the older ssh-rsa signature type and diffie-hellman-group-exchange-sha256 key exchange algorithm, both scheduled for brownouts on 4 November and 9 December before GitHub removes them for good on 13 January 2027.
Why it matters: existing keys already on file keep working for now, but any new RSA key you generate for a deploy key, CI runner or personal machine needs to clear 3072 bits today or the upload fails. If you’re still issuing 2048-bit RSA keys from an old script or image, this is the point it breaks. Worth checking key length on anything you plan to rotate before January, when the older signature and key-exchange algorithms stop working entirely.