Symmetric key cryptography is a fundamental cryptographic technique used to secure information by employing a single shared secret key for both encryption and decryption processes. In this method, the same key is used by both the sender and the receiver to encode and decode the data, hence the term "symmetric."

The core principle behind symmetric key cryptography is that the key serves as a mathematical algorithmic tool to scramble the original data into an unreadable format (encryption) and then unscramble it back into its original form (decryption) when needed. This key must be kept secret, as anyone with access to it can decrypt the protected data.

Advantages of symmetric key cryptography include efficiency and speed. Because the same key is used for both encryption and decryption, the process is generally faster than its counterpart, asymmetric key cryptography (also known as public-key cryptography). Symmetric key algorithms are computationally less intensive, making them suitable for encrypting large volumes of data, such as in data storage and communication.

However, the challenge with symmetric key cryptography lies in securely distributing and managing the secret key between communicating parties. If the key is compromised during transmission or storage, the security of the entire system can be compromised. This is known as the key distribution problem, which is one of the main drawbacks of symmetric cryptography.

To address this issue, secure key exchange protocols and key management systems are employed to ensure that the shared key remains confidential. Additionally, symmetric key cryptography is commonly used in conjunction with asymmetric key cryptography, where symmetric keys are exchanged securely using asymmetric keys, offering both efficiency and robust security for various applications, including secure communication, data encryption, and network security.