Cryptographic algorithm that uses two different, but mathematically linked, keys — one public and one private. The public key — which can be shared with anyone — is used to encrypt data. The private key — which must be kept secret — is required to decrypt data. The security of the algorithm lies in the difficulty of factoring large integers that are the product of two large prime numbers. While it’s easy to multiply them, the time required to determine the original prime numbers from the total is prohibitive, even with today’s computers.