Cryptography

The concept of public-key cryptography was invented by Whitfield Diffie and Martin Hellman, and independently by Ralph Merkle.Their contribution to cryptography was the notion that keys could come in pairs—an encryption key and a decryption key—and that it could be infeasible to generate one key from the other. Diffie and Hellman first presented this concept at the 1976 National Computer Conference ; a few months later, their seminal paper “ New Directions in Cryptography ” was published. ...

Hash A hash is a one-way function that maps data of any arbitrary length to an output digest of fixed length, where it is computationally infeasible to find the input from the output. The values returned by a hash function are often known as Message digest, hash values, hash codes, hash sums, checksums, or simply hashes. Hash functions are keyless and provide the data integrity service. They are usually built using iterated and dedicated hash function construction techniques. A hash function compresses data to a fixed size, which could be considered a shortened reference to the original data. The hash function should be easy to compute but hard to invert for compression, hash functions usually utilize a one-way function of number theory; hence, they are irreversible. Consequently, it is infeasible to reconstruct specific data when a hash value is known. A hash is a one-way function because it cannot be reversed. We can think of a hash as a digital fingerprint of data that is input into it. These types of hash functions are used in many ways. They can be used for authentication, indexing data into hashed tables, checksums, and digital signatures. An example of an SHA256 hash looks like this, 4UsOw2gKuwzwFpY2UH8cDnfMOqHM7Gv5XZBFxDnV4Ww. ...