DSA (Digital Signature Algorithm) is also an asymmetric cryptosystem. It was developed in 1991 to be used as a more secure standard for federal government purposes.
DSA is not used on the same level as RSA. DSA is used specifically for digital signatures. Essentially, the algorithm verifies the authenticity and integrity of the message. DSA uses a combination of a private key and a hash as the main portions of a digital signature. Regardless of a file type or size, the hash is only five to twenty symbols long. A hash is used to authenticate the message. If the message is altered, interrupted, or faked, the hash will change slightly to represent changes. This means that verification is as simple as checking the hash received against the hash sent.