Schemes for Digital Signatures

Abstract

Integrity is the property of information concerning protection against its unauthorized modifications and forgeries. This chapter discusses bulletin board (BB), hash functions, MACs (Message Authentication Codes) and digital signatures, as schemes for maintaining integrity of data. BBs protect data by simply disclosing them to the public, i.e. an entity cannot modify them without being watched by others. Hash functions, Macs, and digital signatures protect data by detecting illegitimate modifications while attaching values to the data. Namely, when an entity illegitimately modifies the data, the modified results become inconsistent with the attached values. When hash functions, MACs and digital signatures are compared regarding the ability to convince entities that the data are authorized ones, hash functions cannot enable entities to convince others, and by MACs, entities can convince others only when relevant secrets are properly protected. On the other hand, digital signatures enable anyone to convince others without constraints.