Encryption is a method to protect data against unauthorized access. Actually, encryption protects data that might be accessed, for example, in an IT environment by sniffing. By applying encryption methods to data, that data is turned into a form that is not easy to interpret without the decryption key. To turn encrypted data back into the original form you need to apply the appropriate decryption method. Thus, unauthorized persons may obtain encrypted data, but if they do not know the appropriate decryption method, they cannot access and use the original data. Of course, authorized persons must be the only persons who have access to the required decryption method.
Almost all encryption methods use a special parameter, the so-called key. To decrypt an encrypted message, you need to know which encryption method was used (or which corresponding decryption method is to be used) and additionally you need to know the correct key to make decryption work correctly. With modern encryption methods, the key is usually a character string of a defined length. For example, encryption methods may use 44-bit keys, 56-bit keys, 128-bit keys or even longer keys. The length of the key affects the security level of an encryption method. The most simple, but also a very time consuming way to crack a key is to try out each possible combination of characters. This method is called “brute force attack”. The longer the key, the more possible combinations you have to try out. That is why short keys are cracked more quickly than long keys. To reduce the time required to crack a key, some programs use a dictionary because most users build their keys or passwords from real words. But the design of an encryption method also plays an important role and some methods with shorter keys are harder to crack than other methods using longer keys. As computers become more and more powerful, the time required to try out a number of different combinations decreases and approved encryption methods become obsolete after some time. Basically, there are two kinds of encryption methods,
symmetric encryption methods and
asymmetric encryptions methods.
With symmetric encryption methods, the sender encrypts his message or data with the same key the receiver uses to decrypt the data. The problem with symmetric encryption methods is that the sender not only has to transfer the encrypted data to the receiver, but also the key which is required to decrypt the data. The transmission of the key from the sender to the receiver requires additional security measures.