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Security Fundamentals & Crypto · Foundational

Rivest-Shamir-Adleman (RSA)

Asymmetric algorithm based on the difficulty of factoring large integers, used for encryption and digital signatures.

Definition

RSA (1977) generates key pairs from two large primes. It is used for signatures, certificate keys, and legacy key transport. NIST recommends at least 2048-bit keys, with 3072 bits for 128-bit security; RSA is vulnerable to Shor's algorithm on a large quantum computer.

Example

openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:3072 -out key.pem

Exam tip

RSA key transport lacks forward secrecy, which is why TLS 1.3 removed it in favor of ephemeral (EC)DHE.

Don't confuse it with

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