## Thursday, August 29, 2019

### Cryptology Assignment Example | Topics and Well Written Essays - 2500 words

Cryptology - Assignment Example Hash functions are arguably the most important of all the encryption algorithms since they help in the prevention of external attacks. They are usually used in most of the applications that require very high security. They are also widely used in the specification of most communication protocols like IPsec and WAP. They typically serve message authentication codes and also help in provision of digital signatures or in some cases, they generate random numbers. MD5 and SHA-1 are the most common of the hash functions (Biham and Chen, 2004). MD5 Algorithm Data filling The MD5 algorithm usually adds the supplement immediately after inputting of the data thereby making the whole length of the mod 512=448. This can be represented as K*512+448 BITS WHERE K IS an integer. Add length Usually, a sixty four bit data b is used to dente the original length of the data while an independent b is used to two thirty two bit blocks. In the event that b>264, we will have to extend the length to multiple s of five hundred and twelve. This implies that the length will become times of sixteen double bytes. MD5 algorithm usually saves the data in an array. The syntax of such an array is given by M [0Ã¢â‚¬ ¦N-1] Where N is in time of sixteen. Initialing of variables If four thirty two but variable named A, B, C, and D were to be defined, they would be initialized as A=0*01234567, B=0/889abcdef, C=0*fedcba98 and D=0*76543210. In this case, the data will be output in the same sequence that is, A, B, C, D. SHA-1 Algorithm This is also an important hash algorithm which is actually based on the MD4 principle. The algorithm actually produces 160 bit output which means that SHA-1 usually needs a set of five thirty two bit registers. However, the similarity between SHA-1 and MD5 is that both of them use a similar approach to message digesting. The SHA-1 algorithm has a total of four distinct rounds of iterative. Each of these rounds has its own twenty steps of operations. If you were to initial ize five variables namely A, B, C, D, and you would have:- A= 0x67452301 B=0xefcdab89 C=0x98badcfe D=0x10325476 E=0xc3d2e1f0 SHA-1 was traditionally thought to be the most secure hash algorithm and it is probably one of the main reasons why it is the current FIPS secure hash standard (Merkle,1990). Principle of operation of the two algorithms Generally the design of the hash algorithms is usually based on the Merkle-Damgard iterative structure. This is since the structure allows for arbitrary length in the messages that are sent. The hash algorithms typically work by dividing the input into different blocks of predetermined lengths. Each of the blocks that are formed is then affixed to the previous state using a form of a compression function in order to compute the updated state. This entire process is usually referred as chaining of a variable. After the processing of the message is completed, the output is given as the last step of the process. The state

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