RSA turns multiplication’s ease and factorization’s difficulty into a division of authority.

RSA encryption and decryption is a public-key cryptographic method that secures data using a matched pair of mathematically related keys. The public key can be shared openly and used to encrypt information, while the private key is kept secret and used to decrypt it. RSA relies on the difficulty of factoring very large numbers, making reversal impractical without the private key when suitable key sizes are used. The same mathematics also supports digital signatures, allowing recipients to verify who signed a message and whether it was altered. It is used primarily in secure communications, digital signatures, and identity authentication.