The Vernam Cipher, also known as the "One-Time Pad," is a powerful and unbreakable encryption technique known for its exceptional security when used correctly. It falls under the category of symmetric encryption, where both the sender and recipient share the same secret key.
In this method, each letter of the plaintext is combined with the corresponding letter from a secret key of the same length, using a bitwise XOR (exclusive OR) operation. The secret key, often referred to as the "pad," is a string of truly random characters.
The critical feature of the Vernam Cipher is that the pad must be truly random, and it must be used only once for a single message. This means that no part of the pad should be reused, and it should remain secret from anyone trying to intercept the message.
The strength of the Vernam Cipher lies in its perfect secrecy if used correctly. When the pad is random, never reused, and stays a secret between the sender and recipient, breaking the encryption becomes mathematically impossible.
Due to the strict requirements for generating and distributing truly random keys of equal length to the messages, as well as the need to use each key only once, the Vernam Cipher is most practical for specific scenarios where the highest level of security is paramount, such as military communications or extremely sensitive data protection.