Symmetric key encryption requires the same key to be used to encrypt and decrypt a text. With asymmetric encryption, a different key is used to decrypt a text to the one used to encrypt it. Symmetric encryption systems require that the key be shared, which is a hazardous process because if anyone intercepts the transmission of the key, the encryption is worthless. With asymmetric encryption, the encryption key needs to be kept private. However, the decryption key can be made public. Therefore, these are called the private key and the public key. It is impossible to work out the private key if you have the public key. Therefore, the recipient of an encrypted text can be sure that the declared sender actually created the encrypted text because the related public key decrypts it. For this reason, asymmetric encryption systems are often used for authentication.