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Symmetric encryption, or secret key encryption as it is usually called, uses a common key and the same cryptographic algorithm to scramble and unscramble the message as shown in Figurel. The security of the transmitted data depends on the fact that eavesdroppers with no knowledge of the key are unable to read the message. One problem with symmetric encryption is the security of the keys which must be passed from the sender to the receiver. 334 uses two different keys; one to scramble the message, and another one to unscramble the message Symmetric Encryption Public Key Encryption Secret Key Encryption Hash Function OOOO -- 2 3