# What is RSA Encryption?

In order to transmit message privately and secretly, a process of encryption and decryption is used. Encryption changes the original message, referred to as *plaintext*, into ciphertext. Decryption turns the ciphertext back to plaintext, so that the recipient of the message can read it. Encryption of messages that are transmitted over networks has become important, particularly as more and more messages are passed over the Internet. RSA encryption is one type of encryption used in this process.

RSA encryption, also called *Rivest-Shamir-Adleman encryption*, was invented by Ronald L. Rivest, Adi Shamir, and Leonard M. Adleman, who were all faculty members at MIT in 1977 and came up with the encryption system that is most commonly referred to using only the first initial of each of their surnames. It has come to be used in Public Key Cryptography (PKC), which is also called the *Public-Key Encryption* system, or alternatively *Asymmetric Encryption*. There is a different type of system called *Symmetric-Key Encryption* .

Public Key Cryptography is a system that is freely available for use on the Internet through a program called PGP (Pretty Good Privacy). PGP, designed by Phil Zimmerman in 1991 to help protect privacy, is available as freeware for some uses. The PKC system uses two keys: a public key and a private key. While the private key is known only by the user’s computer, the public key is shared by each user’s computer with other computers that want to communicate with it in a secure way.

In order to send a message to another computer, the sender’s computer asks for its public key and uses it to encrypt the message. When the receiver’s computer receives a message that has been encrypted with RSA encryption and its own public key, it uses its private key to decrypt it. In other words, the public key is used for encoding, and the private key is used for decoding. A message could be intercepted or hijacked by someone who was not the intended recipient, but not decoded and read.

In March of 2010, the University of Michigan reported a claim that RSA encryption had been cracked by three of their computer scientists. The method used was causing a fluctuation in a server’s power supply. Some have protested that having access to a particularly configured device and tampering with it is not equivalent to breaking the encryption.

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