XKCP: The eXtended Keccak Code Package (or the Xoodoo and Keccak Code Package, in both cases abbreviated as XKCP) is a repository that gathers different free and open-source implementations of the cryptographic schemes defined by the Keccak team. This includes the Keccak sponge function family and closely related variants, such as the SHAKE extendable-output functions and SHA-3 hash functions from FIPS 202, the cSHAKE, KMAC, ParallelHash and TupleHash functions from NIST SP 800-185, the Ketje and Keyak authenticated encryption schemes, the fast KangarooTwelve extendable-output function, the Kravatte pseudo-random function and its modes, as well as the Xoodoo permutation and the Xoofff pseudo-random function and its modes (experimental), the Xoodyak scheme (submission to the NIST lightweight crypto standardization process). The code in this repository can be built as a library called libXKCP.