Which hashing algorithm produces a message digest that is 128 bits long?

The hashing algorithm that produces a message digest that is 128 bits long is MD5. This algorithm is widely used in various applications, including data integrity checks and digital signatures.

MD5 processes input data and generates a fixed-size hash value of 128 bits (or 16 bytes), often represented as a 32-character hexadecimal number. Despite its historical popularity, it is important to note that MD5 is considered to have vulnerabilities, particularly with collision attacks, which compel security professionals to recommend more secure alternatives for cryptographic purposes, such as SHA-256 or SHA-3.

In contrast, the other mentioned options produce different hash lengths: CRC-32 generates a 32-bit hash, SHA-1 produces a 160-bit hash, and SHA-512 yields a 512-bit hash. Understanding the lengths and characteristics of different hashing algorithms is crucial in identifying their appropriate applications in security and data integrity.