Symmetric-key ciphers such as AES and 3DES use the same secret key
for both encryption and decryption, so sender and receiver must share
the same key. Public-key ciphers such as RSA use a public key for encryption
and a secret, private key for decryption. This means that any party
can use the public key to encrypt a message such that it is readable only
by the holder of the private key. The fastest technique known for breaking
established ciphers such as AES and RSA is brute force search of the
space of possible keys, which is made computationally infeasible by the
use of large keys.Most encryption for confidentiality uses symmetric-key
ciphers due to their vastly superior speed, while public-key ciphers are
usually reserved for authentication and session key establishment.