Symmetric Cryptography is a branch of cryptography in which a cryptographic system or algorithms use the same cryptographic key for both encryption and decryption of ciphertext. The keys may be identical or there can be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. This requirement that both parties have access to the secret key is one of the main drawbacks of symmetric key encryption, in comparison to public-key encryption (also known as asymmetric key encryption).
Source: CNSSI 4009, SANS
Related Terms: Asymmetric Encryption or Public Key Encryption