Symmetric key algorithm is a type of encryption method where the same key is used for both encryption and decryption of data. This key must be shared and kept secret between the communicating parties to ensure secure data transmission. Symmetric key algorithms are known for their efficiency and speed, making them suitable for encrypting large amounts of data. Common examples include AES (Advanced Encryption Standard) and DES (Data Encryption Standard). The primary challenge with symmetric key algorithms is securely distributing and managing the encryption keys.

In contrast, an asymmetric key algorithm uses a pair of keys: a public key for encryption and a private key for decryption. Asymmetric methods address the key-sharing challenge by allowing secure communication without requiring the parties to share a single secret key.