RSA

RSA type of public-key cryptography widely used for data encryption of e-mail and other digital transactions over the Internet. RSA is named for its inventors, Ronald L. Rivest, Adi Shamir, and Leonard M. Adleman, who created it while on the faculty at the Massachusetts Institute of Technology.

Introduced at the time when the era of electronic email was expected to soon arise, RSA implemented two important ideas:

1. Public-key encryption. This idea omits the need for a “courier” to deliver keys to recipients over another secure channel before transmitting the originally-intended message. In RSA, encryption keys are public, while the decryption keys are not, so only the person with the correct decryption key can decipher an encrypted message. Everyone has their own encryption and decryption keys. The keys must be made in such a way that the decryption key may not be easily deduced from the public encryption key.

2. Digital signatures. The receiver may need to verify that a transmitted message actually originated from the sender (signature), and didn’t just come from there (authentication). This is done using the sender’s decryption key, and the signature can later be verified by anyone, using the corresponding public encryption key. Signatures therefore cannot be forged. Also, no signer can later deny having signed the message.

This is not only useful for electronic mail, but for other electronic transactions and transmissions, such has fund transfers. The security of the RSA algorithm has so far been validated, since no known attempts to break it have yet been successful, mostly due to the difficulty of factoring large numbers n = pq, where p and q are large prime numbers.