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**A**dleman) A highly secure public key cryptography method by RSA Security, Inc., Bedford, MA (www.rsa.com). Developed in the late 1970s, RSA uses a two-part key. The private key is kept secret but the public key can be made available to anyone.

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 that holds an RSA-encrypted DES key and DES-encrypted data. The RSA method encrypts the secret DES key only to transmit it over the network, but the actual message is encrypted and decrypted using the faster DES algorithm.

**Also for Digital Signatures**

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.

**Also Built Into Hardware**

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

**Secret Key vs. Public Key**

The secret key method uses the same key to encrypt and decrypt but the problem is safely transmitting the secret key to the other side. The public key method is used to send the secret key.