Author: misamaliraza94
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Example
An example of generating RSA Key pair is given below. (For ease of understanding, the primes p & q taken here are small values. Practically, these values are very high). de = 29 × 5 = 145 = 1 mod 72 Encryption and Decryption Once the key pair has been generated, the process of encryption…
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RSA Analysis
The security of RSA depends on the strengths of two separate functions. The RSA cryptosystem is most popular public-key cryptosystem strength of which is based on the practical difficulty of factoring the very large numbers. If either of these two functions are proved non one-way, then RSA will be broken. In fact, if a technique…
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RSA Cryptosystem
This cryptosystem is one the initial system. It remains most employed cryptosystem even today. The system was invented by three scholars Ron Rivest, Adi Shamir, and Len Adleman and hence, it is termed as RSA cryptosystem. We will see two aspects of the RSA cryptosystem, firstly generation of key pair and secondly encryption-decryption algorithms. Generation of RSA Key Pair…
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Public Key Encryption
Public Key Cryptography Unlike symmetric key cryptography, we do not find historical use of public-key cryptography. It is a relatively new concept. Symmetric cryptography was well suited for organizations such as governments, military, and big financial corporations were involved in the classified communication. With the spread of more unsecure computer networks in last few decades,…
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Counter (CTR) Mode
It can be considered as a counter-based version of CFB mode without the feedback. In this mode, both the sender and receiver need to access to a reliable counter, which computes a new shared value each time a ciphertext block is exchanged. This shared counter is not necessarily a secret value, but challenge is that…
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Output Feedback (OFB) Mode
It involves feeding the successive output blocks from the underlying block cipher back to it. These feedback blocks provide string of bits to feed the encryption algorithm which act as the key-stream generator as in case of CFB mode. The key stream generated is XOR-ed with the plaintext blocks. The OFB mode requires an IV…
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Cipher Feedback (CFB) Mode
In this mode, each ciphertext block gets ‘fed back’ into the encryption process in order to encrypt the next plaintext block. Operation The operation of CFB mode is depicted in the following illustration. For example, in the present system, a message block has a size ‘s’ bits where 1 < s < n. The CFB…
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Cipher Block Chaining (CBC) Mode
CBC mode of operation provides message dependence for generating ciphertext and makes the system non-deterministic. Operation The operation of CBC mode is depicted in the following illustration. The steps are as follows − Analysis of CBC Mode In CBC mode, the current plaintext block is added to the previous ciphertext block, and then the result…
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Block Cipher Modes of Operation
In this chapter, we will discuss the different modes of operation of a block cipher. These are procedural rules for a generic block cipher. Interestingly, the different modes result in different properties being achieved which add to the security of the underlying block cipher. A block cipher processes the data blocks of fixed size. Usually,…
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Encryption Process
Here, we restrict to description of a typical round of AES encryption. Each round comprise of four sub-processes. The first round process is depicted below − Byte Substitution (SubBytes) The 16 input bytes are substituted by looking up a fixed table (S-box) given in design. The result is in a matrix of four rows and…