Digital signatures protect the integrity of the signed document and undeniably authenticate the signer individual(s). The weakest link in the chain authenticating the signer is the assumption that only the legal owner can possess the secret key, however we cannot check whether really he/she is the one, who uses the key. The project aims the development of a fingerprint user authentication based algorithm that can only prepare the secret key - stored encoded - for signing if the fingerprint of the legal owner is present. This way even if the secret key is stolen it still cannot be directly used for creating false signatures.