Similarity in source code is identified by searching digital fingerprints representing at least control flow of blocks of programming statements. At least some of the source code is converted into a plurality of respective tokens. Each of the tokens is associated with a plurality of blocks. Tokens are modified by normalizing at least one value in at least one of the blocks and/or by defining at least one abstraction. Thereafter, a representation of control flow is created, and a digital fingerprint representing at control flow of a token is generated. Thereafter, source code within at least one block of a given token is determined and identifiable as being a duplicate of source code stored in a repository by comparing at least one of the generated digital fingerprints and at least one previously generated digital fingerprint.