Introduction to the
International Data Encryption Algorithm, or IDEA, is a common development tool.
Today I will give you a detailed introduction of IDEA.
Introduction of the IDEA
The IDEA, which is called International Encryption Standard in Chinese, was originally called Improved Proposed Encryption Standard (IPES). It is a symmetric key encryption algorithm, originally proposed by James Massey and Xuejia Lai in 1991.
The goal is to replace the DES algorithm. IDEA is a revision of the earlier PES. IDEA is an optional algorithm of the OpenPGP standard.
Idea’s patent expired in 2012, and it is now free to use.
The IDEA of principle
The IDEA encryption block length is 64bits, the key length is 128bits, and is a combination of eight rounds of transformation and half round of output transformation. The process of encryption and decryption is similar. Let’s look at the basic flowchart of IDEA:
In the figure above, the blue circle is the XOR XOR operation, and the green box is the addition module 216. The red dots are multiplicative 216 + 1, which will be converted to 216 if the input is both 0 (0x0000) and 0 (0x0000) if the input is 216.
After eight rounds of operation, the output of the following half round is converted, as shown below (the exchange of the middle two values cancels out the exchange at the end of the last round, so there is no net swap) :
Generation of the IDEA subkey
IDEA uses a LAI-Massey structure. Six 16-place keys are used in each round, and four subkeys are used in the last half round, for a total of 52 subkeys in 8.5 rounds.
The first 8 subkeys are extracted directly from the key, because the key length is 128bits, which is just enough to be divided into 8 16bits self-keys. In the first round, K1 is the 16-bit key.
More sets of eight subkeys are created by moving the master key 25 bits to the left between each of the eight groups.
This article has been included in http://www.flydean.com/idea/
The most popular interpretation, the most profound dry goods, the most concise tutorial, many you do not know the tips to wait for you to discover!
Welcome to pay attention to my public number: “procedures those things”, understand technology, more understand you!