A Symmetric Key is a cryptographic key that is used to perform both the cryptographic operation and its inverse, for example to encrypt plaintext and decrypt ciphertext, or create a message authentication code and to verify the code. Also, a cryptographic algorithm that uses a single key (i.e., a secret key) for both encryption of plaintext and decryption of ciphertext.
Related Term: Secret Key
Source: CNSSI 4009
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