Cryptography for Mail and Data

Cryptography for Mail and Data

Would you put confidential information on a postcard and send it to your friends, colleagues, or business partners? Well, no. But why would you put confidential information in an e-mail and send it around the world?
Lars Packschies
Source: Hakin9 1/2006

What you will learn…

  • how you set up and use your keys Gnu PG,
  • how you can encrypt data on the filesystem level.

What you should know…

  • symmetric and asymmetric cryptography basics,
  • algorithm basics.

Cryptography not only makes your Internet communication more secure by giving you the opportunity to encrypt and/or sign messages, it also guarantees your own privacy. You may for example be aware of the fact that the European Union now regulated the retention of connection data by Internet Service Providers and Mobile Phone Companies for at least 6 months. Together with credit and bonus card data and all the information that lies around, this allows the generation of complete personal profiles not only from the primary data but also from data derived from data mining algorithms. They may already have gathered quite a lot of information about you and your habits but you now could start doing something about it.

Symmetric and asymmetric ciphers

The term cryptography originates from the Greek words kryptós for hidden and gráphein for writing. In general, we distinguish symmetric and asymmetric cryptographic ciphers. The terms symmetric or asymmetric relate to the structure of the key. To encrypt data, or a message respectively, you need the information of how to encrypt or decrypt data (the cipher) and a key, which is the secret parameter in the cipher. The knowledge of that key enables you to encrypt or decrypt information. The key can be used for a a longer period of time or you may use one key for every single message you send. Symmetric cryptographic keys are characterized by the fact that the keys for encrypting and decrypting data are identical (or the key for encrypting and decrypting messages can be calculated from each other). In other words, sender and receiver of the message to be exchanged have to have the same key. And they have to exchange that key prior to sending messages around. This has always been the major drawback of symmetric methods: The so-called key exchange problem.

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