Cryptographic vulnerabilities: Key as IV, insecure HMAC comparison#58
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mdipierro merged 2 commits intoweb2py:masterfrom Feb 10, 2013
mwielgoszewski:master
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Cryptographic vulnerabilities: Key as IV, insecure HMAC comparison#58mdipierro merged 2 commits intoweb2py:masterfrom mwielgoszewski:master
mdipierro merged 2 commits intoweb2py:masterfrom
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Cryptographic vulnerabilities: Key as IV, insecure HMAC comparison
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I defined
AES_newas a function that returns an AES cipher object and a new secure random IV if None was specified. If an attacker can exhibit control over any ciphertext fed to the decrypter, recovering the secret key is a trivial exercise as described in Key as Initialization Vector.See the following gist for an example showing how this can be exploited.
I also noticed
compare()provides a contant-time comparison function for comparing HMAC signatures, however was never called anywhere. This patch updates thesecure_loads()function to usecompare()when comparing HMAC signatures.