How to Revoke SSH Key

Method 1: Manual Removal

ssh username@server "nano ~/.ssh/authorized_keys"

Delete the line with the key.

Method 2: Using sed

ssh username@server "sed -i '/REVOKED_KEY_COMMENT/d' ~/.ssh/authorized_keys"

Method 3: Using SSH CA Revocation List

ssh-keygen -k -f revoked-keys -u key-to-revoke.pub
# On server: add RevokedKeys /etc/ssh/revoked-keys in sshd_config

Method 4: Force Key Expiry with Expiry Date

# Add before key in authorized_keys
command="echo 'Key expired'",expiry-time=YYYYMMDDHHMMSS ssh-rsa AAA...