If I have a file that is allegedly “encrypted using AES algorighm,” can I verify that their statement is correct?
Only if you have a key. (and IV)
Encryption creates arbitrary sequences of bytes; most algorithms do not have any characteristics about their output.
In fact, you can create encrypted text that matches two different plaintexts using two different keys or algorithms .
However, depending on what kind of file it is, it may have a plaintext header that defines the encryption algorithm (and this header may lie).
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