Damien Miller (djm @) in OpenSSH is an enhancement that should help protect against various side-channel attacks, such as , and . The added protection aims to prevent the recovery of the private key residing in memory through side-channel data leaks.
The essence of the protection is that private keys, when not in use, are encrypted using a symmetric key derived from a relatively large 'prekey' consisting of random data (currently its size is 16 KB).
From an implementation perspective, private keys are encrypted when loaded into memory and are then automatically and transparently decrypted when used for signing or when saved/serialized.
For a successful attack, the adversaries must accurately reconstruct the entire prekey before they can attempt to decrypt the protected private key. However, the current generation of attacks has such a bit-recovery error rate that the aggregate of these errors makes correct recovery of the prekey unlikely.
Source: opennet.ru
