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Security Fundamentals & Crypto · Advanced

ElGamal

Asymmetric encryption and signature scheme based on the discrete logarithm problem, an extension of Diffie-Hellman.

Definition

ElGamal encryption produces ciphertext twice the size of the plaintext and is probabilistic. It is used in GNU Privacy Guard as an encryption option and inspired DSA. It is vulnerable to Shor's algorithm like other discrete-log systems.

Example

Older GnuPG keys pair a DSA signing key with an ElGamal encryption subkey.

Exam tip

Recognize ElGamal as a discrete-log asymmetric algorithm alongside DH and DSA.

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