Digital Signatures
- a digital signature of a message (which is produced by the signer) gives a recipient very strong reason to ensure:
- message authentication - message originated from the stated signer
- message integrity - message has not been changed
related: MIC
Digital Signature Algorithms
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Digital Signature Algorithms |
Description |
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ANY Keyed Cryptographic Hash Functions (does not produce true digital signatures) |
secure/keyed hash functions generating HMACs could be used in place of “digital signatures”, but does not protect against non-repudiation (where 1 of the 2 parties that share the same key could secretly sign a message and say it was signed from the other) |
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asymmetric key function can be used for generating digital signatures, and does not fail on non-repudiation
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DSS is simply a document that describes the signing procedure and specifies certain standards | |
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ElGamal Signature Scheme is a digital signature scheme which is based on the difficulty of computing discrete logarithms | |
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DSA is a variant of the Schnorr and ElGamal Signature Schemes DSA is a cryptographic algorithm that generates keys, signs data, and verifies signatures |
Digital Signature Attacks and Forgeries
Digital Signature Attacks
- key-only attack - attacker knows sender’s public key
- known message attack - attacker has access to set of messages and their corresponding signatures
- generic chosen message attack - attacker choose a list of messages independent of sender’s public key)
- directed chosen message attack - attacker choose a list of messages dependent on sender’s public key before signatures are seen
Digital Signature Forgeries
- total break - attacker determines senders private key
- universal forgery - attacker efficiently finds a way to sign arbitrary messages
- selective forgery - attacker forges signature for a chosen message
- existential forgery - attacker forges signature for at least 1 message. attacker has no control over message