Algorithms

Overview

Table 1: Algorithms implemented in MCCrypt Pro

In many applications it wouldn't be a very good idea anymore to use the Data Encryption Standard (DES). The reason for that is the too small key length of 56 bits. Data that is encrypted with DES is not secure. The problem of the key length was solved by the use of Triple DES (3DES). However, because DES was developed primarily for encryption hardware the algorithm is relatively inefficient in the implementation in software. Triple DES is in addition, through the triple useuse of the DES algorithm an extremely slow encryption method. The block size used by DES (and some other known algorithm) is 64 bits. This facilitates additional attacks, if larger amounts of data are encrypted.
Therefore the U.S. National Institute of Standards and Technology (NIST) called for a successor algorithm, that was named Advanced Encryption Standard (AES). The requirements for AES were, that it should be faster and at least equally secure as Triple DES. AES should use 128 bits (16 bytes) blocks and support a key length of 256 bits (at which 128 bits and 192 bits must also be supported). Rijndael, Serpent, Twofish, RC6 and MARS belong to the finalists of the AES selection process. Rijndael was selected by the NIST after a careful inspection of the algorithm for the AES. Rijndael will replace the DES - late Triple DES - in many cryptographic applications in the next years.

In MCCrypt Pro is among other algorithms also the Rijndael algorithm implemented.

MCCrypt Pro offers some further algorithms that provide a compareable security to the Rijndael (Exception Serpent, XOR...). Serpent surpasses the security of Rijndael but it is slower and therefore it got by the NIST in the AES selection process only place 2. Serpent was implemented for AES with a block size of 16 bytes (128 bits) and a key length of 128 to 256 bits. RC6 is the fastest algorithm. The implementation which was done for the AES selection is slightly weaker than Rijndael.

The AES candidates which are implemented in MCCrypt Pro and which reached the the final selection round are Rijndael, Serpent, Twofish, RC6. Algorithms in this round were expected to be secure, that means no weaknesses were found. There are currently no attacks that are applicable on these algorithms that are more effective than a Bruthforce Attack to break them. All AES algorithms were defined for key lengths of 128 to 256 bits. Twofish surpasses the security of Rijndael temporarily (shorter key lengths than 256 bits) and reached in the AES selection process place 3.

There are also no known attacks against Blowfish. Blowfish did not become a AES candidate because beside other characteristics of the algorithm it's block size is only 8 bytes. This is regarded as too small if one encrypts great amounts of data. The security of Blowfish is not compared officially with AES. Blowfish has a high security level and it also became an alternative to the use of DES. Blowfish does not achieve, however, the security level of the five of AES finalists. But it keeps up and can be compared with the other AES candidates. (AES candidate became his successor Twofish)

The XOR algorithms are weak at short key lengths. The strength of the XORBlock algorithm can be adjusted with two parameters: InternalRounds and ExternalRounds. The XORStream algorithm has one parameter, the InternalRounds. It is recommended at both of them to use at least the value 4. The security of these algorithms was not examined yet.The key length should be maximized in order to provide an acceptable security level.

Specific information to the encryption algorithms

Related Content:

• MCCrypt Lite Algorithms
• MCCrypt ActiveX DLL Algorithms
• MCCipher ActiveX DLL Algorithms
• MCRijndael ActiveX DLL Algorithms
• MCCrypt Lite
• MCWipe
• MCSign
• MCVerify