What is a One-Time Pad?
A one-time pad is a type of encryption algorithm used in cryptography, where the key that encrypts and decrypts the message is used only one time. Obviously, a one-time pad, sometimes shortened to OTP, is not the most efficient use of resources. The one-time pad requires just as many resources to create it as a multiple-use key, but it must be destroyed after one use. When proper procedures are followed, however, the OTP is impossible to break because each one is different, making it worthwhile to create in certain situations. Essentially, cryptography is the process of hiding information, and a one-time pad is a tool used to hide the data inside a code. When using cryptography, one person would encrypt a message, which involves applying an OTP or another type of key to the message. The person receiving the message would then use the key to decrypt and read the message. Many people think of cryptography only as a method by which governments and military groups create a code for disguis
A one-time pad, sometimes called the Vernam cipher, uses a string of bits that is generated completely at random. The keystream is the same length as the plaintext message and the random string is combined using bitwise exclusive-or with the plaintext to produce the ciphertext. Since the entire keystream is random, an opponent with infinite computational resources can only guess the plaintext if he sees the ciphertext. Such a cipher is said to offer perfect secrecy and the analysis of the one-time pad is seen as one of the cornerstones of modern cryptography. While the one-time pad saw use during wartime, over diplomatic channels requiring exceptionally high security, the fact that the secret key (which can be used only once) is as long as the message introduces severe key-management problems. While perfectly secure, the one-time pad is impractical. Stream ciphers (see Question 86) were developed as an approximation to the action of the one-time pad, and while contemporary stream ciphe
A one-time pad, sometimes called the Vernam cipher, uses a string of bits that is generated completely at random. The keystream is the same length as the plaintext message and the random string is combined using bitwise exclusive-or with the plaintext to produce the ciphertext. Since the entire keystream is random, an opponent with infinite computational resources can only guess the plaintext if he sees the ciphertext. Such a cipher is said to offer perfect secrecy and the analysis of the one-time pad is seen as one of the cornerstones of modern cryptography. While the one-time pad saw use during wartime, over diplomatic channels requiring exceptionally high security, the fact that the secret key (which can be used only once) is as long as the message introduces severe key-management problems. While perfectly secure, the one-time pad is impractical. Stream ciphers were developed as an approximation to the action of the one-time pad, and while contemporary stream ciphers are unable to p
A one-time pad is a very simple yet completely unbreakable symmetric cipher. “Symmetric” means it uses the same key for encryption as for decryption. As with all symmetric ciphers, the sender must transmit the key to the recipient via some secure and tamperproof channel, otherwise the recipient won’t be able to decrypt the cipher text. The key for a one-time pad cipher is a string of random bits, usually generated by a cryptographically strong pseudo-random number generator (CSPRNG). It is better to generate the key using the natural randomness of quantum mechanical events (such as those detected by a Geiger counter), since quantum events are believed by many to be the only source of truly random information in the universe. One-time pads that use CSPRNGs are open to attacks which attempt to compute part or all of the key. With a one-time pad, there are as many bits in the key as in the plaintext. This is the primary drawback of a one-time pad, but it is also the source of its perfect
