Signcryption and Advanced Signature Topics
Stub. Beyond full-domain-hash signatures (already covered): an RSA-based signature scheme with a tight security proof, PKCS1 signatures and Bleichenbacher's forgery attack on them, signcryption (combining signing and encryption into one primitive, via encrypt-then-sign/sign-then-encrypt/Diffie-Hellman-based constructions), forward secrecy and non-repudiation as additional desirable properties, certificates and the public-key infrastructure (coping with malicious CAs, revocation), legal aspects of digital signatures, and forward-secure signatures.
Corresponds to Chapter 13 (the signature definition and full-domain- hash/RSA signatures are already covered in digital-signatures-and-pki). Covers a tighter-security-proof RSA signature variant, PKCS1’s padded-RSA signature standard and Bleichenbacher’s forgery attack against careless PKCS1 implementations, and signcryption — a single primitive providing both confidentiality and authenticity more efficiently than naively composing separate encryption and signature schemes, built via encrypt-then-sign, sign-then-encrypt, or directly from Diffie-Hellman, with forward secrecy and non-repudiation as the extra properties a good signcryption/signature deployment should provide. Rounds out the public-key-infrastructure side (certificate authorities, what goes wrong when one is malicious or negligent, and certificate revocation) with the legal status of digital signatures and forward-secure signatures (limiting the damage a single key compromise can do to past signatures) as closing topics.
Outline (TODO — flesh out each)
- An RSA-based signature scheme with a tight security proof
- Case study: PKCS1 signatures; Bleichenbacher’s attack
- Signcryption — combining signatures and encryption
- Secure signcryption; signcryption as an abstract interface
- Constructions: encrypt-then-sign, sign-then-encrypt
- A Diffie-Hellman-based signcryption construction
- Forward secrecy and non-repudiation
- Certificates and the public-key infrastructure
- Coping with malicious or negligent certificate authorities; revocation
- Legal aspects of digital signatures
- Fun application: forward-secure signatures