Signature forgery attack
A signature forgery attack produces a signature that a verifier accepts as authentic without authorization from the legitimate signer's private key.
Hacking Cryptography
A signature forgery attack attempts to create a valid signature for data without authorization from the holder of the signing private key.
- How it is used
- Frames signature security around attacks that bypass authorization while preserving apparent verification.
- How deep it goes
- Traces forgery classes through vulnerable PKCS #1 v1.5 parsing and a complete RSA e=3 exploit, stopping short of broader attacks.
- Examples
- Demonstrates vulnerable Go and Python-RSA verifiers, RSA keys with e=3, cube-root stitching, and a successful forged-signature test.
- What you can do after
- Diagnose padding-verification flaws by comparing legitimate and forged signatures against strict and insecure verifiers.
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Real-World Cryptography
A signature forgery attack is an attack that produces a signature a verifier accepts without knowledge of the legitimate signer's private key.
- How it is used
- Warns how flawed RSA signature verification can let attackers produce signatures accepted without private-key knowledge.
- How deep it goes
- Explains the threat and implementation distinction, but stops short of constructing the forgery or detailing attack variants.
- Examples
- Uses RSA signing and verification diagrams plus Bleichenbacher's attack and misimplemented open-source verifiers as examples.
- What you can do after
- Evaluate RSA PKCS#1 v1.5 deployments and treat backward compatibility as a reason for heightened caution.
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Related concepts
- rsaes-pkcs1-v1_5uses · RSAES-PKCS1-v1_5 is a PKCS #1 standard RSA encryption scheme that formats messages with type 2 padding before encryption.
- Bleichenbacher's e=3 forgery attackincludes · Bleichenbacher's e=3 forgery attack is an RSA signature-forgery attack that exploits lax validation of PKCS #1 v1.5 signature padding when the public exponent is 3.
- digital signatureaddressed by · A digital signature is cryptographic data generated with a private key and verified with corresponding public information to authenticate data or its signer and detect alteration.
- selective forgery attackincludes · A selective forgery attack enables an attacker to forge valid signatures for messages satisfying specified constraints.
- existential forgery attackincludes · An existential forgery attack produces at least one valid message-signature pair without the attacker needing to choose the message in advance or possess the signing secret.
- universal forgery attackincludes · A universal forgery attack enables an attacker to forge valid signatures for arbitrary attacker-chosen messages.
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