When encrypting a message, the sender transforms the clear text into a secret text. Doing so  requires the following main elements: In modern cryptography, the algorithm is published and known to everyone, whereas the keys  are kept secret. This configuration corresponds to Kerckhoffs’ principle, which is named after  Auguste Kerckhoffs, a Dutch cryptographer, who formulated it in 1883:  “A system should not depend on secrecy, and it should be able to fall into the enemy’s  hands without disadvantage.” In other words, the security of a cryptographic system should depend on the security of the  key, so the key must be kept secret. Therefore, the secure management of keys is the primal  task of modern cryptographic systems.  Adhering to Kerckhoffs’ Principle is done for the following reasons:  GLYPH<SM590000> The  algorithm  is the mathematical or logical formula that is applied to the key and the  clear text to deliver a ciphered result, or to take a ciphered text and deliver the original  clear text.  GLYPH<SM590000> The  key  ensures that the result of the encrypting data transformation by the algorithm is  only the same when the same key is used. That decryption of a ciphered message results  only in the original clear message when the correct key is used. Therefore, the receiver of  a ciphered message must know which algorithm and which key must be used to decrypt  the message. GLYPH<SM590000> It is much more difficult to keep an algorithm secret than a key.  GLYPH<SM590000> It is harder to exchange a compromised algorithm than to exchange a compromised key.  GLYPH<SM590000> Secret algorithms can be reconstructed by reverse engineering software or hardware  implementations. GLYPH<SM590000> Errors in public algorithms can generally be found more easily, when many experts look  into it. GLYPH<SM590000> In history, most secret encryption methods proved to be weak and inadequate. GLYPH<SM590000> When a secret encryption method is used, it is possible that a back door was built in. GLYPH<SM590000> If an algorithm is public, many experts can form an opinion about it. Also, the method can  be more thoroughly investigated for potential weaknesses and vulnerabilities. 6.2.2 Kerckhoffs’ principle 6.2.3 Keys The keys that are used for the cryptographic algorithms often are sequences of numbers and  characters, but can also be any other sequence of bits. The length of a key influences the  security (strength) of the cryptographic method. The longer the used key, the more difficult it  is to compromise a cryptographic algorithm.  For example, the DES (symmetric key) algorithm uses keys with a length of 56 bits,  Triple-DES (TDES) uses keys with a length of 112 bits, and Advanced Encryption Standard  (AES) uses keys of 128, 192, 256, or 512 bits. The asymmetric key RSA algorithm (named  after its inventors Rivest, Shamir, and Adleman) uses keys with a length of 1024 - 4096 bits. 176  IBM 14 Model ZR1 Technical Guide