Digital signatures are the public-key primitives of message authentication. In the physical world, it is common to use handwritten signatures on handwritten or typed messages. They are used to bind signatory to the message. Similarly, a digital signature is a technique that binds a person/entity to the digital data. This binding can be independently verified… Continue reading Cryptography Digital signatures
Message Authentication
In the last chapter, we discussed the data integrity threats and the use of hashing technique to detect if any modification attacks have taken place on the data. Another type of threat that exist for data is the lack of message authentication. In this threat, the user is not sure about the originator of the message.… Continue reading Message Authentication
Whirlpool
This is a 512-bit hash function. Applications of Hash Functions There are two direct applications of hash function based on its cryptographic properties. Password Storage Hash functions provide protection to password storage. Data Integrity Check Data integrity check is a most common application of the hash functions. It is used to generate the checksums on… Continue reading Whirlpool
Popular Hash Functions
Let us briefly see some popular hash functions − Message Digest (MD) MD5 was most popular and widely used hash function for quite some years. Secure Hash Function (SHA) Family of SHA comprise of four SHA algorithms; SHA-0, SHA-1, SHA-2, and SHA-3. Though from same family, there are structurally different. RIPEMD The RIPEMD is an… Continue reading Popular Hash Functions
Properties of Hash Functions
In order to be an effective cryptographic tool, the hash function is desired to possess following properties − Design of Hashing Algorithms At the heart of a hashing is a mathematical function that operates on two fixed-size blocks of data to create a hash code. This hash function forms the part of the hashing algorithm.… Continue reading Properties of Hash Functions
Cryptography Hash functions
Hash functions are extremely useful and appear in almost all information security applications. A hash function is a mathematical function that converts a numerical input value into another compressed numerical value. The input to the hash function is of arbitrary length but output is always of fixed length. Values returned by a hash function are… Continue reading Cryptography Hash functions
Data Integrity in Cryptography
Until now, we discussed the use of symmetric and public key schemes to achieve the confidentiality of information. With this chapter, we begin our discussion on different cryptographic techniques designed to provide other security services. The focus of this chapter is on data integrity and cryptographic tools used to achieve the same. Threats to Data… Continue reading Data Integrity in Cryptography
ElGamal Analysis
In ElGamal system, each user has a private key x. and has three components of public key − prime modulus p, generator g, and public Y = gx mod p. The strength of the ElGamal is based on the difficulty of discrete logarithm problem. The secure key size is generally > 1024 bits. Today even 2048 bits long key… Continue reading ElGamal Analysis
Encryption and Decryption
The generation of an ElGamal key pair is comparatively simpler than the equivalent process for RSA. But the encryption and decryption are slightly more complex than RSA. ElGamal Encryption Suppose sender wishes to send a plaintext to someone whose ElGamal public key is (p, g, y), then − C1 = gk mod p C2 =… Continue reading Encryption and Decryption
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… Continue reading Example