The word cryptography is derived from the Greek words "kryptos" (hidden) and "graphein" (to write). Cryptography is the science concerned with securing messages. Cryptanalysis describes the art of covertly deciphering encrypted messages, i.e. making their content legible. Summarising, the branch of mathematics which comprises cryptography and cryptanalysis is denoted as cryptology. Non-secured data are denoted as plaintext, secured data as cipher or coded text. The process of converting plaintext to ciphertext is described as enciphering (also, encrypting). The reverse process, the conversion of ciphertext into plaintext is described as deciphering (decoding).

Even in the classical antiquity, messages were encrypted to protect them from foreign eyes. Caesar, for example, exchanged the individual letters of the Latin alphabet according to a simple rule so that the text looked, for the uninitiated, like a meaningless mixture of letters. Thanks to computer technology, today's cryptography can resort to quite different, significantly more intricate and secure processes.

Today, the private man and small businesses can use means to protect their interests which just tens of years ago would not even have been available to big secret services. Security authorities and secret services are not happy with the fact, however, that good cryptographic processes are available for everyone. They fear that "organized crime" could hatch their sinister plans behind the protection of cryptography and that criminal regimes could plan acts of war and terror unhindered. For this reason, governments and their authorities have continually attempted to hinder the use of cryptographic processes. Such attempts, however, do not only affect criminal organisations but also the individual citizen in his right to informational self-determination and in his basic, guaranteed right to privacy in communication. On account of this, there is continually controversial discussion between state protectors and civil rights activists.

There is certain information, both in occupational and in private life, which has to be protected against unauthorised access and manipulation. Enciphering techniques may therefore not only be something which is used in the demimonde of secret services and gangsters but increasingly in everyday life as only enciphering can guarantee secure communication and data storage.

Important, on the other hand, is the realisation that data can not be protected from unauthorised access alone through the acquisition of enciphering software. Even the best software can not guarantee security if the environment of its use is not right. The image of the chain which is only as strong as its weakest link is also applicable to the organisation of processes which are sensitive to security. For this reason, it is not possible to achieve security alone through certain selected measures but it is necessary to analyse the process as a whole and direct it towards security. Here, the costs for the organisation of the environment will often exceed those for the software alone by far. The best enciphering software is useless if an attacker reaches the key used through manipulation of the computer system (e.g. with a so-called Trojan horse). Alongside the internal computer or network security, however, the human environment plays a big part. If the opponent can guess only a few of the details of a key used for enciphering, this is possibly sufficient for him to reconstruct the plaintext. Also, the best enciphering process cannot make up for notes lying around openly containing "secret" keys.

For the decision as to how a system is realised taking security aspects into consideration, the costs will continually have to weighed up against the usefulness. For this, the following question has to be answered first of all: how important is my need for security to me? The cryptograph, Bruce Schneier, is of the opinion that there are really only two types of cryptographic methods: "one stops your little sister from reading your data", and the other is the serious one. If you come to the conclusion that enciphering of the type "little sister" is adequate, then act correspondingly and buy a simple enciphering product! But don't think that it cannot be cracked only because you cannot crack it yourself. No matter what: don't pay a lot of money for such a product! Today namely, you can get products of the serious category for very little money (e.g., on this site).