Well the question is as simple as that . Because I recently noticed that the openssh-server uses AES-CTR for the symmetric encryption and I wondered why ? From what I heared AES-CTR is a block cipher mode that can be run in parallel , but GCM has a built in integrity check and is a stream cipher mode . So why does HTTPS use GCM in almost any scenarios and SSH not ?
asked Mar 4, 2018 at 11:35
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1CTR and GCM are both modes that turn a block cipher into a stream cipher. Note that CTR, as used by OpenSSH, is still authenticated because of its use of HMAC. CTR with HMAC is likely to be compatible with a wider range of clients than GCM.– forestCommented Mar 5, 2018 at 3:23
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