Asymmetric encryption methods use different keys for the encryption and the decryption of a message. The sender generates a keypair, messages encrypted with one of these keys can only be decoded with the other one. One of these keys will be designated as the private key, this will be used to encrypt the messages. The other key, called public key is made available to anyone the sender wishes to send messages to. Anyone having access to the encrypted message and the public key can read the encrypted message and be sure that it was created with the appropriate private key. Certain encryption algorithms (like RSA) make it also possible to encrypt a message using the public key, in this case only the owner of the private key can read the message. The disadvantage of asymmetric encryption is that it is relatively slow and computation intensive. A suitable infrastructure for exchanging public keys is also required; this is needed to verify the identity of the sender, confirming that the message is not a forgery. This topic is discussed in Section 11.1.1.3, Authentication and public key algorithms The length of the keys used in asymmetric encryption ranges from 512 to 4096 bits.