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**R**ural

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MSA.

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**R**ivest-

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**A**dleman) A highly secure cryptography method by RSA Security, Inc., Bedford, MA (www.rsa.com), a division of EMC Corporation since 2006. It uses a two-part key. The private key is kept by the owner; the public key is published.

Data are encrypted by using the recipient's public key, which can only be decrypted by the recipient's private key. RSA is very computation intensive, thus it is often used to create a digital envelope, which holds an RSA-encrypted DES key and DES-encrypted data. This method encrypts the secret DES key so that it can be transmitted over the network, but encrypts and decrypts the actual message using the much faster DES algorithm.

RSA is also used for authentication by creating a digital signature. In this case, the sender's private key is used for encryption, and the sender's public key is used for decryption. See digital signature.

The RSA algorithm is also implemented in hardware. As RSA chips get faster, RSA encoding and decoding add less overhead to the operation. See cryptography and digital certificate.

**Secret Key Vs. Public Key**

The secret method uses the same key to encrypt and decrypt. The problem is transmitting the key to someone so they can use it. The public key method uses two keys. One kept secret and never transmitted, and the other made public. Sometimes the public key method is used to send the secret key of the private method, and then the message is sent using the private key method.