A symmetric key is a cryptographic key used for both encrypting and decrypting information within a symmetric encryption scheme. In this approach, the same key is shared between the sender and the recipient, and both must possess this secret key to securely exchange information.
When data is encrypted with a symmetric key, only someone with that exact key can decrypt and access the original information. This method is also referred to as secret key encryption, private key cryptography, or symmetric cryptography.
How Symmetric Key Encryption Works
• Key Generation: A secret key is generated, often as a random string of bits, numbers, or characters.
• Encryption: The sender uses this key and a symmetric encryption algorithm (such as AES or DES) to convert plaintext (readable data) into ciphertext (scrambled, unreadable data).
• Decryption: The recipient, who also possesses the same key, uses it to decrypt the ciphertext back into its original readable form.
Key Characteristics
• Single Key Use: Both encryption and decryption use the same key, unlike asymmetric encryption, which uses a public/private key pair.
• Shared Secret: The key must be kept secret and shared securely between parties. If an unauthorized person gains access to the key, they can decrypt all protected data.
• Efficiency: Symmetric key algorithms are generally faster and less computationally intensive than asymmetric algorithms, making them suitable for encrypting large volumes of data.
Common Algorithms
• Block ciphers: Encrypt data in fixed-size blocks (e.g., AES, DES).
• Stream ciphers: Encrypt data one bit or byte at a time (e.g., RC4, ChaCha20)