in 1978 in Martin Gardner's Scientific American column, and the algorithm came to be known as RSA, from their initials. RSA uses exponentiation modulo a product of two very large primes, to encrypt and decrypt, performing both public key encryption and public key digital signatures. Its security is connected to the extreme difficulty of factoring large integers, a problem for which there is no known efficient general technique (though prime factorization may be obtained through brute-force attacks; this grows much more difficult the larger the prime factors are). A description of the algorithm was published in the Mathematical Games column in the August 1977 issue of Scientific American. Since the 1970s, a large number and variety of encryption, digital signature, key agreement, and other techniques have been developed, including the Rabin cryptosystem, ElGamal encryption, DSA - and elliptic curve cryptography. See also Books on cryptography GNU Privacy Guard Identity-based encryption (IBE) Key escrow Key-agreement protocol PGP word list Post-quantum cryptography Pretty Good Privacy Pseudonym Public key fingerprint Public key infrastructure (PKI) Quantum computing Quantum cryptography Secure Shell (SSH) Symmetric-key algorithm Threshold cryptosystem Web of trust Notes References . The first two sections contain a very good introduction to public-key cryptography. IEEE 1363: Standard Specifications for Public-Key Cryptography Christof Paar, Jan Pelzl, "Introduction to Public-Key Cryptography", Chapter 6 of "Understanding Cryptography, A Textbook for Students and Practitioners". (companion web site contains online cryptography course that covers public-key cryptography), Springer, 2009. External links Oral history interview with Martin Hellman, Charles Babbage Institute, University of Minnesota. Leading cryptography scholar Martin Hellman discusses the circumstances and fundamental insights of his invention of public key cryptography with collaborators Whitfield Diffie and Ralph Merkle at Stanford University in the mid-1970s. An account of how GCHQ kept their invention of PKE secret until 1997 Anonymity networks Cryptographic software Cryptographic protocols Banking technology Public key infrastructure Network architecture