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I'm working on an encryption project. Basically, I have some samples of the input values and output values. Both of them are in Hex numbers. The input is a 16 byte Hex sequence and the output is a 64-byte Hex sequence.But there is number in the two sequence.

Can it be cipher code?

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closed as off-topic by e-sushi Aug 5 '17 at 4:57

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  • $\begingroup$ I'm not sure what you mean by 'there is number in the two sequence'? But yes, this could easily be an encryption even though the output is longer than the input, e.g. a block cipher with block size of 32 bytes, so that your input gets padded to 32 bytes to encrypt, and a 32 byte random IV. If you're asking if you can determine the encryption algorithm and key from one sample input and output then no. $\endgroup$ – Rup Aug 4 '17 at 23:43
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Any sized data can be cipher code, that the output is a multiple of 16 in binary does make it more plausible that it is a cipher code.

64 hexadecimal digits means 32 bytes or 256 bits. That makes SHA-256 a logical choice, but it could also be AES-256 in CBC mode prefixed with a 16 byte IV, a HMAC value, etc.

As the output of most cryptographic primitives will be indistinguishable from random the only thing you can do is try - by hasing the input or performing any keyed operation with a given key, of course.

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