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Asymmetric encryption
In asymmetric encryption (also known as 'public key cryptography') a pair of keys is used: a private key and a public key. The private key is kept secret and never divulged to anyone, including the actual person that owns it. The public key is made publicly available to those the owner chooses. Generally it is with the public key that messages are encrypted and with the private key that they are decrypted, but that is not always the rule. What is constant is that the two keys are co-relational, so that data encrypted with one key (be that the public or private key) can only be decrypted with the other. It is, however, impossible to derive a private key from the public key.
At the root of any asymmetric encryption method is a ‘hard to solve’ mathematical problem from which a common number between two separate ends is arrived. Asymmetric encryption algorithms are thus computationally intensive and generally slower than symmetric encryption algorithms; therefore, they are commonly used as authentication techniques. An example of an authentication technique could be when the private key is used to encrypt a data packet and its accompanying digital signature. In this case, the data receiver uses the related public key to decrypt the two. Authentication of the sender is thus proven because only someone in possession of the secret private key can generate a packet and signature that can be decrypted with that particular public key.
Public keys can typically be distributed in the form of X.509 certificates.
Related terms:
Algorithm, CA, Digital Certificate, Encryption, Key, Symmetric encryption, X.509
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