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# What Is the RSA Algorithm?

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• Written By: Mary Elizabeth
• Edited By: Bronwyn Harris
2003-2014
Conjecture Corporation
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The word algorithm is believed to be a variant of algorism, which refers to Arabic numeration and derives from the last name of an Arabic mathematician named Muhammad ibn-Musa al-Khwarizmi. In cryptography, an algorithm is a process or procedure that, when followed, produces a particular type of encryption, and may be referred to as an encryption algorithm. Message encryption is key to the safe transmission or messages on the Internet. There are a number of different encryption algorithms, including Rijndael, MARS, RC6, Serpent, and Twofish, all of which were submitted as candidates for the AES (Advanced Encryption Standard), which is used for secure communications over the Internet. RSA algorithm is another encryption algorithm, employed in another encryption system used on the Internet, notably, for email.

Ronald L. Rivest, Adi Shamir, and Leonard M. Adleman, faculty members at MIT, invented the Rivest-Shamir-Adleman — popularly known as the RSA algorithm by using the first letter of each of their last names — in 1977. The RSA algorithm has come to be used in the Public-Key Encryption system, also known as Public Key Cyptography or PKC. Encryption systems can have one or two keys. The PKC is an asymmetric encryption system, meaning that it has two keys.

Although previously known the U.S. National Security Agency earlier, Public-Key Cryptography was separately invented and made public in 1976 by Whitfield Diffie of Sun Microsystems® and Martin Hellman of Stanford University. They figured out a way to avoid the sender having to include the encryption key with the message, as is necessary in symmetric key encryption. This was a great advance, because sending the key with the message raised the risk of possible interception and decrypting. As of March, 2010, a claim surfaced that computer scientists at the University of Michigan had cracked the RSA algorithm, but it has also been pointed out that the method depends on tampering with the computer, not figuring out how to decrypt any message at any time from anywhere in the world.

The PKC system works in several steps. First, the sender's computer asks the recipient computer to provide its public key. If it responds, the receiver’s public key — created by the RSA algorithm — is used to encrypt the message. Then the message is sent, and when the receiver’s computer receives the message, the receiver’s private key is used for decrypting the message. Since there are two keys, an intercepted message or a message that is hijacked is safe because it cannot be decrypted without the key.