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Decryption , with a similar meaning also deciphering , but especially in cryptology with different definitions also deciphering , describes in a broader sense the explanation or interpretation of unknown characters , symbols , images, notes or other artifacts or their conversion into known characters.

Different reasons for decryption can be distinguished:

  • The technical application of standardized (known) coding procedures.
  • There is only an unknown coding or language, but the author did not want to hide any information.
  • A transfer, use or modification of data that the author wanted to prevent.
  • Disclosure of information or messages from persons other than the addressees desired by the author .

Most computer science applications do not focus on the decryption of unknown codes, but rather encryption and decryption for technical functions, such as data compression or the conversion of different character sets .

Decryption in cryptology

The plain text is generated from a ciphertext through decryption with the help of a secret key

In the narrower sense, especially in Cryptology , the decryption of the process in which a previously Ver encryption cipher text (often called ciphertext hereinafter) using a decryption method and key in the clear text is converted back. A clear distinction is made between encryption and decryption on the one hand and decoding on the other.

Accordingly, decryption is the authorized activity of the legitimate recipient, who is in possession of the key and thus extracts the plain text from the ciphertext; deciphering, on the other hand, is the (usually unauthorized) activity of a cryptanalyst who tries to find out the message content without knowing the key and uses cryptanalytic methods to do so .

Decryption in archeology

The term decryption is used in archeology for the interpretation or translation of unknown writing systems and characters .

Decryption and copyright

Decryption has gained current importance in the context of circumventing copy protection or other mechanisms that are set up by companies to protect the copyrights of multimedia content (e.g. CDs, DVDs and Pay TV ). In particular, cryptological methods, so-called encryption methods , are used for this purpose.

Legal situation in Germany

With the introduction of Section 95a as part of an amendment to the German Copyright Act (UrhG) a few years ago, the use of technical facilities - commonly referred to as "circumvention devices" - with which a copyright holder installed copy protection can be circumvented, was at least in principle prohibited (§ 95a Abs. 1 UrhG).

Individual evidence

  1. High Command of the Wehrmacht : General key rules for the Wehrmacht. Berlin 1944, p. 5 f. (PDF, 0.9 MB; last accessed on August 26, 2010)