Encryption schemes, whether symmetric or asymmetric, solve the problem of secure communications over an insecure network. Digital signatures solve a different problem, analogous to the purpose of a pen-and-ink signature on a physical document. It is thus interesting that the tools used to construct digital signatures are very similar to the tools used to construct asymmetric ciphers.
- NIST–DSS, Digital Signature Standard (DSS). FIPS Publication 186-2, National Institue of Standards and Technology, 2004. http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf