01 BTC cryptology principle

Catalog

Preface

The principle of cryptography in bitcoin

1. Hash

2. Signature

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Preface

Learn from teacher Xiao Zhen's 《 Blockchain technology and Application 》 Open class notes , For learning reference .

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The principle of cryptography in bitcoin

1. Hash

• Hash function used in cryptography （crypotographic hash function）

The hash function used in cryptography has two important properties

1. collision resistance（ Anti collision ）

   collision Refers to hash collision ：x≠y H(x)=H(y) Two different inputs , The output is equal . Because the input space is always larger than the output space , Therefore, it is inevitable . Unless violence solves , It's hard to base on x find y.

   It has been proved by people's practical experience , Hash collisions are not human made .

2. hiding（ Irreversible ）

      The calculation process of hash function is unidirectional and irreversible . The premise of this property is that the input space is large enough , More evenly distributed .

The above two properties are combined , Can be realized digital commitment ( Also known as digital equivalent of a sealed envelope)：

The predicted results X Enter the calculated hash value Y, Publish hash value Y, Finally X. In the process X Cannot be tampered with .

• Hash function used in bitcoin

The hash function used in bitcoin adds a property on the basis of cryptography ：

puzzle friendly （ unpredictable ）

That is, the calculation of hash value is unpredictable

2. Signature

Opening an account in bitcoin is to create a public-private key pair locally (public key ,private key), From asymmetric encryption technology .

In information exchange, public key is used to encrypt and verify signatures , The private key is used to decrypt and sign , Public key and private key are different from each other . When the public key and private key are the same , For symmetric encryption . In asymmetric encryption technology, the public key is like the card number of our bank card , The private key is the password of our bank card , If others transfer money to us, they only need to know our bank card number .

But a good random source is needed when generating public and private keys and signatures , Prevent the generation of the same public and private keys or the disclosure of private keys .