Which hash function has an output size of 160 bits?

The hash function that has an output size of 160 bits is SHA-1. SHA-1, which stands for Secure Hash Algorithm 1, was developed by the National Security Agency (NSA) and published by the National Institute of Standards and Technology (NIST) in 1995. Its design allows it to create a fixed-size hash value of 160 bits (20 bytes) from any input data size, making it suitable for various applications like digital signatures and integrity verification.

In contrast, MD5 generates a 128-bit hash output, making it shorter than SHA-1. The MD6 function is not widely recognized as it remains a candidate in the SHA-3 competition and does not have a standard output size. SHA-256, part of the SHA-2 family, produces a 256-bit hash output, which also surpasses the size of SHA-1. Thus, SHA-1 is the correct choice due to its specific 160-bit output size.