What purpose does hashing data serve in digital signatures?

Hashing data plays a crucial role in the functioning of digital signatures by transforming variable-length input (the original data) into a fixed-length output, known as a hash value or hash code. This is fundamental because it enables a streamlined method for ensuring data integrity and authenticity.

When a digital signature is created, the hash of the original message is computed, and this hash is then encrypted using the sender’s private key. The recipient can verify the signature by decrypting it with the sender's public key and comparing the decrypted hash with the hash generated from the received message. If both hashes match, it confirms that the message has not been altered in transit and establishes the authenticity of the sender.

This fixed-length representation simplifies the processing and comparison of the data while also providing a unique fingerprint for the original content. If any modification occurs, even a tiny change in the original data will result in a significantly different hash output, making it easy to detect alterations. This capability is essential for ensuring data integrity in secure communications.