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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 using the recipient's public key, which can only be decrypted by the recipient's private key. RSA is more computation intensive than the secret key method, which uses the same key at both ends. Thus, RSA is often used to send the secret key to the other end so that the faster method can be used to decrypt large amounts of data. See secret key cryptography, digital envelope and DES.

**For Digital Signatures**

RSA is used to authenticate a digital file 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.

**For Cryptocurrencies**

The public key, which is pseudonymous and freely published, is used to receive assets, while the private key, which must be kept secret, is used for sending assets. See crypto keys.

**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.