Find encryption algorithm from a file

If I have a file claimed to be "encrypted using AES algorighm", c开发者_C百科an I verify that their claim is true?

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Only if you have the key. (and IV)

Encryption produces arbitrary byte sequences; most algorithms do not have any characteristics about their output.

In fact, one can design a ciphertext which corresponds to two different plaintexts using two different keys or algorithms.

However, depending on what the file is, it may have a (plaintext) header specifying the encryption algorithm (and that header may be lying).

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Good encryption schemes are actually designed to hide away all the details of encryption from the encrypted data so if they used a proper application to do the encryption, you should not be able to verify the algorithm used.