Digital Signature Algorithm (DSA)

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Digital Signature Algorithm (DSA) uses a combination of modular exponentiation and discrete logarithms to generate a digital signature given a public and private key pair.

• proposed in 1991 by NIST as part of its Digital Signature Standard (DSS) proposal
• 4 versions of DSA
• patented by US gov
  • makes it available royalty-free worldwide
• supports full verification of authentic signatures
  • provides authentication, integrity, and nonrepudiation
• used in Botan, Bouncy Castle, OpenSSL, and wolfCrypt

How It Works

• uses a 4 step process:
  1. Key generation
     • consists of parameter generation and then computation of a per-user pair of public and private keys based on those parameters
  2. Key distribution
  3. Signing
  4. Signature verification
• is extremely sensitive to the entropy, secrecy, and uniqueness of the random signature value that is used during the signing process
  • violating any one of these cryptologic requirements can end up revealing the entire private key
  • this vulnerability is also present in ECDSA
    • elliptic curve variant of DSA
    • famously exploited by overflow group’s attack on Sony PS3 console