Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

This question already has an answer here:

I have the following question about TLS security:

Assume TLS-PSK protected HTTP with AES256-CBC cipher. When a TLS connection is established, client sends some encrypted data, where the plaintext is well known to an attacker.
For example, it can be a HTTP request, like:

GET /some_resource HTTP/1.1
...

Can an attacker use intercepted ciphertext and known plaintext it to reveal the secret key?

Does TLS have any features to protect from that?

share|improve this question

marked as duplicate by e-sushi, figlesquidge, Gilles, rath, archie Apr 27 at 21:10

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1  
Does TLS have any features to protect from that Yes... AES! –  rath Apr 26 at 16:16

1 Answer 1

up vote 2 down vote accepted

This question boils down to, "Are there known-plaintext attacks against AES-256-CBC?" The answer is: No, no such attacks better than brute force are known. This would constitute a catastrophic break in AES-256-CBC, and any cipher broken in such a way would be abandoned rapidly.

share|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.