Recap of Digital Signature Scheme

This chapter has discussed digital signatures, the main cryptographic mechanism for providing non-repudiation of data. While it is possible under special circumstances to produce a ‘digital signature’ using symmetric techniques, digital signature schemes are normally regarded as being public-key primitives.

The main issues we covered were:

• Digital signature schemes are in some senses complementary to public-key encryption schemes, providing data origin authentication and non-repudiation of data based on the belief that only a designated signatory is in possession of a signature key.

• There are two general techniques for designing a digital signature scheme: digital signature schemes with appendix and digital signature schemes with message recovery.

• The most popular digital signature schemes are based on RSA or DSA (ECDSA).

• Digital signatures have different properties and offer different guarantees to handwritten signatures.

We have also seen that, as for all cryptographic primitives, the security of digital signature schemes is intrinsically bound to the effectiveness of the management of the cryptographic keys on which they rely. We will address these challenges in much greater detail.