The challenge involves the topic of encoding and coding theory, as in error correction and compression. (Not to be confused with program source code).
Questions relating to mathematical codes: Huffman encoding, Reed-Solomon encoding, etc. (Not to be confused with program source code)!
If your question is about ciphers, prefer cryptography. If it is about compression, in general prefer compression. This is not mutually exclusive with those tags, but it is more oriented to codes which don't have another related tag.
