MD2 (RFC 1319): 128-bit message digest by Ronald Rivest, used in legacy X.509 certificates. Engine: js-md2, OpenSSL-compatible.
MD4 (RFC 1320): 128-bit message digest, predecessor of MD5, common in NTLM and other legacy protocols. Engine: js-md4, OpenSSL-compatible.
MD2 (RFC 1319) and MD4 (RFC 1320) are early 128-bit message digests by Ronald Rivest, predecessors of MD5.