An MD4 hash is a unique value produced by a mathematical calculation. It provides a 128-bit (16 bytes, 32 hex chars) key from the data input which is claimed to be unique. As such, MD4 hashes are used to ensure data integrity.
MD4 was developed by MIT professor Ronald L. Rivest. It was accepted by the RSA in October 1990.
Both MD4, and its successor MD5, are optimized for 32-bit machines. Its predecessor MD2 was optimized for 8-bit machines. MD4 is known to be fast, but possibly not absolutely secure. On the other hand, MD5 is not as fast as MD4 but offers much more assurance of data security.