Over-encryption

About coding (also via encryption or superencryption ; English superencipherment ; French surchiffrement ) is in the cryptology (mostly second) stage of an additional encryption called.

The term is used in connection with classic methods of cryptography and hand keys , i.e. encryptions carried out manually, often with pencil and paper. With machine keys and especially with modern computer-aided encryption algorithms , which usually consist of many (dozen) encryption rounds anyway, this term is obsolete, since possible over-encryption in this case can also be regarded as an integral part of the method.

principle

Encryption is used to generate a ciphertext from plain text with the help of a key. At about coding this ciphertext is (usually using a different method) a second time encrypted.

After a plaintext using a first method has been encrypted and then a first ciphertext produced  (picture) , is the first ciphertext - mostly using another method - a second time encrypted, which is about coding calls. As a result, improved cryptographic security, that is to say better protection against unauthorized deciphering, is sought and in most cases is also achieved. As a result, the procedure as a whole is usually safer and less easily broken .

history

This method is to be considered primarily from a historical point of view, but can also be observed in the modern age, especially in the case of encryptions to be carried out by hand. The classic is the use of a code book to encrypt messages. In the simplest case, a message such as "Come today" is coded with the code "AAA". Caesar encryption could now be used as the encryption method. By Caesar Key C = 3 would then "AAA" here to "DDD" on down are. Any combination of basic encryption (first level) and over-encryption is conceivable.

Shortly after the First World War , diplomatic codes were overencrypted with the help of so-called " i-worms " (individual worms, meaning random texts made up of sequences of digits). One example is the German process called “ Floradora ” by the British Codebreakers .

During the Second World War , the German Navy used the weather short key , a special code book, to encrypt weather reports. The Enigma machine was used for encryption.

During the Cold War , in the 1950s, the Finnish-Russian agent Reino Häyhänen ( code name : VICTOR; abbreviation: VIC), spying for the Soviet Union , used a special espionage cipher , the VIC cipher , which was even used multiple times.

literature

• Friedrich L. Bauer : Deciphered Secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, ISBN 3-540-67931-6 .

Individual evidence

1. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, pp. 167-169.