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encryptionaesencryption-symmetric

Need help understanding this '||' operation in AES encryption

I have never gone really deep into encryption algorithms till date but now I have been put on a project which demands some knowledge on it.

I am using AES-CTR algo and really need to understand what '||' this operation means.

For example: I have the formula which looks like this:

message = AES-CTR<KEY>(SNONCE16||DNONCE16||SID16,NS14).

Basically, key is the encryption key, snonce16 is randomly generated 16 byte on server side, dnonce16 is received from an IOT device and SID16 is its serial no., NS14 is randomly generated encryption nonce on server side.

I get everything, but what does this operation '||' mean . I assumed it was a normal 'or' operation but that might not be the case.

Really need an experts opinion on this.

Thanks.

Solution

  • In cryptography the || operation usually means simple concatenation. It's written \| (or, apparently \mathbin\Vert) in TeX and that makes the pipe characters much more narrow, distinguishing it more from other uses.

    Related text on the origin of || on the cryptography site is asked and answered here. Apparently it has been adopted from set theory in mathematics.

    Note that usually the (encryption) nonce is put in front of the plaintext or ciphertext, rather than the last parameter, so that surprised me a bit.