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This article mainly introduces the algorithm of block chain cryptography, which is very detailed and has a certain reference value. Friends who are interested must read it!

The cryptographic techniques of block chain include digital signature algorithm and hash algorithm. The digital signature algorithm is a subset of the digital signature standard, which represents a specific public key algorithm that is only used as a digital signature, while the hash algorithm is an algorithm that maps a binary plaintext of any length to a shorter binary string. and different plaintexts are difficult to map to the same hash value.

The operating environment of this tutorial: windows7 system, Dell G3 computer.

Cryptography is the core of block chain technology. The cryptographic techniques of block chain include digital signature algorithm and hash algorithm.

Digital signature algorithm

The digital signature algorithm is a subset of the digital signature standard, which represents a specific public key algorithm that is only used as a digital signature. The key runs on the message hash generated by SHA-1: to verify a signature, to recalculate the message's hash, decrypt the signature using the public key and compare the results. Abbreviated as DSA.

Digital signature is a special form of electronic signature. So far, at least 20 countries have adopted laws to recognize electronic signatures, including the European Union and the United States. China's electronic signature law was adopted at the 11th meeting of the standing Committee of the Tenth National people's Congress on August 28, 2004. Digital signature is defined in the ISO 7498-2 standard as: "some data attached to a data unit, or a cryptographic transformation of a data unit, which allows the receiver of the data unit to confirm the source of the data unit and the integrity of the data unit, and to protect the data from forgery by people (such as the receiver)." The digital signature mechanism provides an authentication method to solve the problems of forgery, repudiation, impersonation and tampering, using data encryption technology and data transformation technology, so that both the sender and the sender can meet two conditions: the receiver can identify the identity claimed by the sender; the sender can not deny the fact that it has sent the data.

Digital signature is an important branch of cryptography. It is proposed to sign electronic documents to replace the handwritten signatures on traditional paper documents, so it must have five characteristics.

(1) the signature is credible.

(2) the signature cannot be forged.

(3) the signature is not reusable.

(4) the signed document is unalterable.

(5) the signature is undeniable.

Hash (hash) algorithm

Hash, that is, any length of input (also known as pre-mapping, pre-image), through the hash algorithm, transformed into a fixed length output, the output is the hash value. This transformation is a compressed mapping, in which the space of the hash value is usually much smaller than the space of the input, and different inputs may be hashed into the same output, but the input value cannot be deduced backwards. To put it simply, it is a function that compresses a message of any length into a message digest of a fixed length.

Hash algorithm, it is an one-way cryptosystem, that is, it is an irreversible mapping from plaintext to ciphertext, only encryption process, no decryption process. At the same time, the hash function can change the input of any length to get a fixed-length output. This one-way feature of the hash function and the fixed length of the output data make it possible to generate messages or data.

Represented by Bitcoin chunk chain, the secondary hash is repeatedly used in the process of workload proof and key coding, such as SHA (SHA256 (k)) or RIPEMD160 (SHA256 (K)). The advantage of this approach is to increase the workload or increase the difficulty of cracking without knowing the protocol.

Represented by Bitcoin blockchain, the two main hash functions used are:

1.SHA-256, mainly used to complete PoW (proof of workload) calculation

2.RIPEMD160, which is mainly used to generate bitcoin addresses. The process of generating an address from the public key for Bitcoin is shown in figure 1 below.

These are all the contents of this article entitled "what is the algorithm of Block chain cryptography?" Thank you for your reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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