Symmetric-key cryptography uses shared secret key material for cryptographic operations, including encryption and authentication. In a symmetric encryption scheme, a recipient holding the secret key can recover the plaintext from a ciphertext. Keeping the algorithm public does not prevent security: the secret is the key, not the procedure.
For example, a one-time pad encrypts a bit string as and decrypts with . Perfect secrecy requires an independently uniform secret key as long as the message and never reused. Reusing it gives , exposing a relation between messages. Ordinary efficient symmetric ciphers instead offer computational guarantees under stated assumptions. Confidentiality alone does not ensure message integrity; authenticated encryption addresses both.[ref]
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Symmetric-key cryptography, also known as secret-key cryptography, is a type of encryption where the same key is used for both encryption and decryption of data. In this system, both parties involved in communication share a common key, which must remain confidential between them. ### Key Characteristics: 1. **Single Key**: Only one key is used for both encrypting and decrypting messages. This makes it efficient in terms of performance.