RSA

A widely used public-key algorithm for encryption and signatures.

RSA is an asymmetric algorithm whose security rests on the difficulty of factoring the product of two large prime numbers. It supports both confidentiality, by encrypting with a recipient's public key, and authentication, by signing with a private key, and it underpins certificates and key exchange in many TLS deployments. Compared with elliptic curve cryptography, RSA needs much larger keys for equivalent strength, so ECC is often preferred on constrained or mobile devices.