What is RSA encryption?

D5 · Crypto  ·  CompTIA Security+ SY0-701
RSA (Rivest–Shamir–Adleman) is the most widely used asymmetric encryption algorithm. Its security is based on the mathematical difficulty of factoring the product of two large prime numbers.

Key sizes: 2048-bit minimum (current standard), 4096-bit for highest security. 1024-bit is considered broken.

Uses: key exchange (TLS), digital signatures, certificate signing, email encryption (S/MIME).
RSA is slow — used for key exchange and signatures, NOT for bulk data encryption. TLS uses RSA (or ECDH) to exchange a symmetric key, then AES for the actual data. Quantum computers threaten RSA — hence post-quantum cryptography research.
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