区块链使用数字签名机制是什么,区块链使用数字签名机制有哪些

请查看相关英文文档

A. Principle of digital signature

Digital signature is some data attached to the data unit, or a cryptographic transformation of the data unit. This data or transformation allows the recipient of the data unit to confirm the origin of the data unit and the integrity of the data unit and protect the data from forgery by someone (e.g. the recipient).

It is a method of signing messages in electronic form. A signed message can be transmitted in a communication network. Digital signatures can be obtained based on both public key cryptography and private key cryptography, mainly digital signatures based on public key cryptography. Including ordinary digital signatures and special digital signatures.

(1) Blockchain uses digital signature mechanism for further reading:

Implementation method

Digital signature algorithm relies on public key encryption technology to achieve. In public key encryption technology, each user has a pair of keys: a public key and a private key. The public key can be freely released, but the private key is kept secret; another requirement is to make it impossible to derive the private key from the public key.

Common digital signature algorithms include three algorithms:

1. Password generation algorithm;

2. Marking algorithm;

3 .Verification algorithm.

B. How to interpret the digital signature of the blockchain

In the distributed network of the blockchain, communication between nodes and reaching trust require reliance on digital signature technology, which It mainly realizes identity confirmation and information authenticity and integrity verification.

Digital signature

Digital signature (also known as public key digital signature, electronic signature) is a kind of ordinary physical signature similar to written on paper, but uses public key encryption Technical implementation in the field, methods for identifying digital information. A set of digital signatures usually defines two complementary operations, one for signing and another for verification. It is a string of numbers that only the sender of the message can generate that cannot be forged by others. This string of numbers is also an effective proof of the authenticity of the message sent by the sender of the message. Simple proof that “I am who I am”.

C. How does blockchain ensure the security of data in the network?

How does blockchain ensure the security of data in the network:
In blockchain technology Among them, digital encryption technology is the key. Generally, the asymmetric encryption algorithm is used, that is, the password for encryption and the password for unlocking are different. To put it simply, we have an exclusive private key. As long as we protect our private key and give the public key to the other party, the other party will use the public key to encrypt the file to generate ciphertext, and then pass the ciphertext to you, and we will use the private key. Decrypting the plain text can ensure that the transmission content is not seen by others. In this way, the encrypted data transmission is completed!
At the same time, there is also a digital signature that adds an extra layer of protection for us to prove that the document has not been tampered with during the process of sending it to the other party. It can be seen that the encryption technology of blockchain can effectively solve the problem of data circulation and sharing.The safety issues in the process can be said to be of great use. Chaoshe

D. What is a digital signature

Digital signature is an encryption mechanism used to verify the authenticity and integrity of numbers and data. We can think of it as a digital version of the traditional handwritten signature method, and is more complex and secure than signatures.

In short, we can understand a digital signature as a code attached to a message or document. Once a digital signature is generated, it serves as proof that the message has not been tampered with during its journey from sender to receiver.

While the concept of using cryptography to protect the confidentiality of communications dates back to ancient times, digital signature schemes only became a reality in the 1970s with the development of public key cryptography (PKC). So, to understand how digital signatures work, we first need to understand the basics of hash functions and public key cryptography.

Hash is one of the core elements in digital signatures. The operation process of hash value refers to converting data of any length into a fixed length. This is achieved through a special operation called a hash function. The value generated by the hash function is called a hash value or message digest.

When a hash value is combined with a cryptographic algorithm, which uses a cryptographic hash function to generate a hash value (digest), the value acts as a unique digital fingerprint. This means that any change to the input data (message) will result in a completely different output value (hash value). This is why cryptographic hash functions are widely used to verify the authenticity of numbers and data.

Public key cryptography or PKC refers to an encryption system that uses a pair of keys: a public key and a private key. The two keys are mathematically related and can be used for data encryption and digital signatures.

As an encryption tool, PKC has higher security than symmetric encryption. Symmetric encryption systems rely on the same key to encrypt and decrypt information, but PKC uses a public key for data encryption and a corresponding private key for data decryption.

In addition, PKC can also be applied to generate digital signatures. Essentially, the process involves the sender encrypting the hash of the message (data) using its own private key. Next, the recipient of the message can check whether the digital signature is valid using the public key provided by the signer.

In some cases, the digital signature itself may include an encryption process, but this is not always the case. For example, the Bitcoin blockchain uses PKC and digital signatures, and unlike most people believe, there is no encryption in the process. Technically speaking, Bitcoin in turn deploys the so-called Elliptic Curve Digital Signature Algorithm (ECDSA) to verify transactions.

In the context of cryptocurrency, digital signature systems typically consist of three basic processes:Hash, sign and verify.

The first step is to hash the message or data. This is done by operating on the data using a hashing algorithm to generate a hash value (i.e. message digest). As mentioned above, messages can vary greatly in length, but when messages are hashed, their hash values ​​are all the same length. This is the most basic property of hash functions.

However, merely hashing the message is not a requirement to generate a digital signature, since messages that have not been hashed can also be encrypted using the private key. But for cryptocurrency, messages need to be processed by a hash function, because processing fixed-length hash values ​​helps cryptocurrency programs run.

After the message has been hashed, the sender of the message needs to sign their message. Public key cryptography is used here. There are several types of digital signature algorithms, each with its own unique operating mechanism. Essentially, a hashed message (hash value) is signed using a private key, and the recipient of the message can then check its validity using the corresponding public key (provided by the signer).

In other words, if the private key is not used when generating a signature, the recipient of the message will not be able to use the corresponding public key to verify its validity. Both public and private keys are generated by the sender of the message, but only the public key is shared with the recipient.

It is important to note that digital signatures are associated with the content of each message. Therefore, unlike handwritten signatures, digital signatures are different for each message.

Let’s take an example to illustrate the entire process, from the beginning to the final step of verification. Let's assume that Alice sends a message to Bob, hashes the message to a hash value, and then combines the hash value with her private key to generate a digital signature. The digital signature will serve as the unique digital fingerprint of the message.

When Bob receives the message, he can use the public key provided by Alice to check the validity of the digital signature. This way, Bob can be sure that the signature was created by Alice, since only she has the private key corresponding to the public key (at least that's what we assumed).

Therefore, it is important for Alice to keep her private key safe. If another person gets Alice's private key, they can also create a digital signature and pretend to be Alice. In the context of Bitcoin, this means that someone has access to Alice's private keys and can transfer or use her Bitcoins without her knowledge.

Digital signatures are typically used to achieve three goals: data integrity, authentication, and non-repudiation.

Digital signatures can be applied to a variety of digital documents and certificates. Therefore, they have severalapp. Some of the most common cases include:

The main challenges faced by digital signature schemes are mainly limited to the following three factors:

In short, digital signatures can be understood as A specific type of electronic signature that refers to the use of electronic means to sign documents and messages. Therefore, all digital signatures can be considered electronic signatures, but not vice versa.

The main difference between them is the authentication method. Digital signatures require the deployment of cryptographic systems such as hash functions, public key cryptography, and encryption techniques.

Hash functions and public key encryption are the core of digital signature systems and are now used in a variety of cases. When implemented properly, digital signatures can improve security, ensure integrity, and facilitate authentication of all types of data.

In the world of blockchain, digital signatures are used to sign and authorize cryptocurrency transactions. They are especially important for Bitcoin because digital signatures ensure that a token can only be used by someone with the corresponding private key.

While we have been using electronic and digital signatures for years, there is still a lot of room for growth. Today, most official documents are still based on paper materials, but as more systems migrate to digital, we will see more digital signature solutions.

E. [In-depth knowledge] Illustration of the encryption principle of the blockchain (encryption, signature)

First, let’s put an architecture diagram of Ethereum:

In the learning process, we mainly use a single module to learn and understand, including P2P, cryptography, network, protocols, etc. Let’s start with the summary directly:

The problem of secret key distribution is also the problem of secret key transmission. If the secret key is symmetric, then the secret key can only be exchanged offline. If the secret key is transmitted online, it may be intercepted. Therefore, asymmetric encryption is used, with two keys, one private key is kept privately, and the other public key is made public. Public keys can be transmitted over the Internet. No offline transactions required. Ensure data security.

As shown in the figure above, node A sends data to node B, and public key encryption is used at this time. Node A obtains the public key of node B from its own public key, encrypts the plaintext data, and sends the ciphertext to node B. Node B uses its own private key to decrypt.

2. Unable to solve message tampering.

As shown in the figure above, node A uses B's public key to encrypt, and then transmits the ciphertext to node B. Node B uses the public key of node A to decrypt the ciphertext.

1. Due to A’sThe public key is public. Once an online hacker intercepts the message, the ciphertext will be useless. To put it bluntly, this encryption method can be decrypted as long as the message is intercepted.

2. There is also the problem of being unable to determine the source of the message and the problem of message tampering.

As shown in the figure above, before sending data, node A first encrypts it with B's public key to obtain ciphertext 1, and then uses A's private key to encrypt ciphertext 1 to obtain ciphertext 2. After node B obtains the ciphertext, it first decrypts it using A's public key to obtain ciphertext 1, and then decrypts it using B's private key to obtain the plaintext.

1. When data ciphertext 2 is intercepted on the network, since A's public key is public, you can use A's public key to decrypt ciphertext 2 and obtain ciphertext 1. So this seems to be double encryption, but in fact the private key signature of the last layer is invalid. Generally speaking, we all hope that the signature is signed on the most original data. If the signature is placed later, the signature lacks security since the public key is public.

2. There are performance issues. Asymmetric encryption itself is very inefficient, and two encryption processes are performed.

As shown in the figure above, node A is first encrypted with A's private key, and then encrypted with B's public key. After receiving the message, node B first uses B's private key to decrypt it, and then uses A's public key to decrypt it.

1. When ciphertext data 2 is intercepted by a hacker, since ciphertext 2 can only be decrypted using B’s private key, and B’s private key is only owned by node B, others cannot keep it secret. Therefore, the safety is the highest.
2. When node B decrypts and obtains ciphertext 1, it can only use A’s public key to decrypt it. Only data encrypted by A's private key can be successfully decrypted with A's public key. Only node A has A's private key, so it can be determined that the data was transmitted by node A.

After two asymmetric encryptions, the performance problem is serious.

Based on the above problem of data tampering, we introduced message authentication. The encryption process after message authentication is as follows:

Before node A sends a message, it first performs a hash calculation on the plaintext data. A digest is obtained, and then the illumination and original data are sent to Node B at the same time. When node B receives the message, it decrypts the message. Parse out the hash digest and original data, then perform the same hash calculation on the original data to obtain digest 1, and compare the digest and digest 1. If they are the same, they have not been tampered with; if they are different, they have been tampered with.

As long as ciphertext 2 is tampered with during the transmission process, the resulting hash will be different from hash1.

NoneThere is no way to solve the signature problem, that is, both parties attack each other. A never acknowledges the message he sent. For example, A sends an error message to B, causing B to suffer losses. But A denied that he did not send it himself.

In the process of (3), there is no way to solve the problem of mutual attacks between the two interacting parties. What does that mean? It may be that the message sent by A is not good for node A, and later A denies that the message was not sent by it.

In order to solve this problem, signatures were introduced. Here we combine the encryption method in (2)-4 with the message signature.

In the above figure, we use node A's private key to sign the summary information sent by it, then add the signature + original text, and then use B's public key to encrypt. After B obtains the ciphertext, he first uses B's private key to decrypt it, and then uses A's public key to decrypt the digest. Only the content of the two digests is compared to see if they are the same. This not only avoids the problem of anti-tampering, but also circumvents the problem of attacks from both parties. Because A signed the information, it cannot be repudiated.

In order to solve the performance problem when asymmetrically encrypting data, hybrid encryption is often used. Here we need to introduce symmetric encryption, as shown below:

When encrypting data, we use a symmetric secret key shared by both parties to encrypt. The symmetric secret key should not be transmitted on the network to avoid loss. The shared symmetric key here is calculated based on one's own private key and the other party's public key, and then the symmetric key is used to encrypt the data. When the other party receives the data, it also calculates the symmetric secret key and decrypts the ciphertext.

The above symmetric secret key is unsafe because A's private key and B's public key are generally fixed in the short term, so the shared symmetric secret key is also fixed. To enhance security, the best way is to generate a temporary shared symmetric key for each interaction. So how can we generate a random symmetric key during each interaction without transmitting it?

So how to generate a random shared secret key for encryption?

For the sender node A, a temporary asymmetric secret key pair is generated every time it is sent, and then a symmetric secret key can be calculated based on the public key of node B and the temporary asymmetric private key. (KA algorithm-Key Agreement). The symmetric secret key is then used to encrypt the data. The process here for the shared secret key is as follows:

For node B, when receiving the transmitted data, the random public key of node A is parsed. Then use the random public key of node A and the private key of node B to calculateSymmetric key (KA algorithm). The data is then encrypted using a symmetric key.

For the above encryption methods, there are still many problems, such as how to avoid replay attacks (adding Nonce to the message), and problems such as rainbow tables (refer to the KDF mechanism to solve). Due to limited time and ability, I will ignore it for now.

So what kind of encryption should be used?

Mainly based on the security level of the data to be transmitted. Unimportant data can actually be authenticated and signed, but very important data needs to use an encryption scheme with a relatively high security level.

Cipher suite is a concept of network protocol. It mainly includes algorithms for identity authentication, encryption, message authentication (MAC), and secret key exchange.

During the entire network transmission process, algorithms are mainly divided into the following categories according to cipher suites:

Secret key exchange algorithms: such as ECDHE, RSA. Mainly used for authentication when the client and server handshake.

Message authentication algorithm: such as SHA1, SHA2, SHA3. Mainly used for message summarization.

Batch encryption algorithm: such as AES, mainly used to encrypt information flow.

Pseudo-random number algorithm: For example, the pseudo-random function of TLS 1.2 uses the hash function of the MAC algorithm to create a master key - a 48-byte private key shared by both parties in the connection. The master key serves as a source of entropy when creating session keys (such as creating a MAC).

In the network, a message transmission generally needs to be encrypted in the following four stages to ensure safe and reliable transmission of the message.

Handshake/network negotiation phase:

During the handshake phase between both parties, link negotiation is required. The main encryption algorithms include RSA, DH, ECDH, etc.

Identity authentication phase:

In the identity authentication phase, the source of the sent message needs to be determined. The main encryption methods used include RSA, DSA, ECDSA (ECC encryption, DSA signature), etc.

Message encryption stage:

Message encryption refers to encrypting the sent information flow. The main encryption methods used include DES, RC4, AES, etc.

Message identity authentication phase/anti-tampering phase:

Mainly to ensure that the message has not been tampered with during transmission. The main encryption methods include MD5, SHA1, SHA2, SHA3, etc.

ECC: Elliptic CurvesCryptography, elliptic curve cryptography. It is an algorithm that generates public and private keys based on point multiple products on ellipses. Used to generate public and private keys.

ECDSA: used for digital signatures and is a digital signature algorithm. A valid digital signature gives the recipient reason to believe that the message was created by a known sender, so that the sender cannot deny that the message has been sent (authentication and non-repudiation), and that the message has not been altered in transit. The ECDSA signature algorithm is a combination of ECC and DSA. The entire signature process is similar to DSA. The difference is that the algorithm used in the signature is ECC, and the final signed value is also divided into r and s. Mainly used in the identity authentication phase.

ECDH: It is also a Huffman tree secret key based on the ECC algorithm. Through ECDH, both parties can negotiate a shared secret without sharing any secrets, and this shared secret key is the current The communication is temporarily generated randomly, and the secret key disappears once the communication is interrupted. Mainly used in the handshake negotiation phase.

ECIES: is an integrated encryption scheme, also known as a hybrid encryption scheme, which provides semantic security against selected plaintext and selected ciphertext attacks. ECIES can use different types of functions: key agreement function (KA), key derivation function (KDF), symmetric encryption scheme (ENC), hash function (HASH), H-MAC function (MAC).

ECC is an elliptical encryption algorithm, which mainly describes how the public and private keys are generated on the ellipse, and is irreversible. ECDSA mainly uses the ECC algorithm to make signatures, while ECDH uses the ECC algorithm to generate symmetric keys. All three of the above are applications of the ECC encryption algorithm. In real-world scenarios, we often use hybrid encryption (a combination of symmetric encryption, asymmetric encryption, signature technology, etc.). ECIES is a set of integrated (hybrid) encryption solutions provided by the underlying ECC algorithm. This includes asymmetric encryption, symmetric encryption and signature functions.

<meta charset="utf-8">

This precondition is to ensure that the curve does not contain singular points .

Therefore, as the curve parameters a and b continue to change, the curve also shows different shapes. For example:

The basic principles of all asymmetric encryption are basically based on a formula K = k G. Among them, K represents the public key, k represents the private key, and G represents a selected base point. The asymmetric encryption algorithm is to ensure that the formula cannot be inverted (that is, G/K cannot be calculated). *

How does ECC calculate the public and private keys? Here I describe it according to my own understanding.

I understand that the core idea of ​​ECC is to select a base point G on the curve, then randomly pick a point k on the ECC curve (as the private key), and then calculate our public key based on k G K. And ensure that the public key K is also on the curve. *

So how to calculate k G? How to calculate k G to ensure that the final result is irreversible? This is what the ECC algorithm is supposed to solve.

First, we randomly select an ECC curve, a = -3, b = 7 and get the following curve:

On this curve, I randomly select two points. How to calculate the multiplication of points? We can simplify the problem. Multiplication can be expressed by addition, such as 2 2 = 2+2, 3 5 = 5+5+5. Then as long as we can calculate addition on the curve, we can theoretically calculate multiplication. Therefore, as long as addition calculations can be performed on this curve, multiplication can be calculated theoretically, and the value of expressions such as k*G can also be calculated theoretically.

How to calculate the addition of two points on the curve? Here, in order to ensure irreversibility, ECC has customized an addition system on the curve.

In reality, 1+1=2, 2+2=4, but in the ECC algorithm, the addition system we understand is impossible. Therefore, it is necessary to customize a set of addition systems suitable for this curve.

The definition of ECC is to randomly find a straight line in the graph and intersect the ECC curve at three points (or possibly two points). These three points are P, Q, and R respectively.

Then P+Q+R = 0. Among them, 0 is not the 0 point on the coordinate axis, but the infinity point in ECC. In other words, the infinity point is defined as point 0.

Similarly, we can get P+Q = -R. Since R and -R are symmetrical about the X-axis, we can find their coordinates on the curve.

P+R+Q = 0, so P+R = -Q, as shown in the figure above.

The above describes how addition operations are performed in the world of ECC curvesof.

As can be seen from the above figure, there are only two intersection points between a straight line and a curve, which means that the straight line is the tangent line of the curve. At this time, P and R coincide.

That is, P = R. According to the above-mentioned ECC addition system, P+R+Q = 0, it can be concluded that P+R+Q = 2P+Q = 2R+Q=0

So we get 2 P = -Q (is it getting closer to the formula K = k G of our asymmetric algorithm?).

So we come to the conclusion that multiplication can be calculated, but it can only be calculated at the tangent point, and it can only be calculated by 2.

If 2 can be turned into any number for multiplication, then it means that multiplication can be performed in the ECC curve, then the ECC algorithm can meet the requirements of an asymmetric encryption algorithm.

So can we calculate the multiplication of any random number? The answer is yes. That is the dot product calculation method.

Choose a random number k, then what is k * P equal to?

We know that in the computer world, everything is binary. Since ECC can calculate the multiplication of 2, we can describe the random number k as binary and then calculate it. Suppose k = 151 = 10010111

Since 2 P = -Q, so k P is calculated. This is the dot product algorithm. Therefore, multiplication can be calculated under the ECC curve system, so this asymmetric encryption method is feasible.

As for why this calculation is irreversible. This requires a lot of deduction, and I don't understand it either. But I think it can be understood this way:

Our watches usually have time scales. Now if we take 0:00:00 on January 1, 1990 as the starting point, and if we tell you that a full year has passed until the starting point, then we can calculate the current time, that is, we can calculate it on the watch. The hour, minute and second hands should point to 00:00:00. But conversely, I said that the hour, minute and second hands on the watch are now pointing to 00:00:00. Can you tell me how many years have passed since the starting point?

The ECDSA signature algorithm is basically similar to other DSA and RSA, both using private key signature and public key verification. It’s just that the algorithm system uses the ECC algorithm. Both parties interacting must adopt the same set of parameter systems. The signature principle is as follows:

Select an infinity point on the curve as the base point G = (x, y). Randomly pick a point k on the curve as the private key, and K = k*G to calculate the public key.

Signature process:

Generate a random number R and calculate RG.

According to the random number R, the HASH value H of the message M, and the private key k, Calculate the signature S = (H+kx)/R.

Send the message M, RG, S to the receiver.

Signature verification process:

Receive message M, RG, S

Calculate the HASH value H according to the message

According to the sender For the public key K, calculate HG/S + xK/S, and compare the calculated result with RG. If equal, the verification is successful.

Formula inference:

HG/S + xK/S = HG/S + x(kG)/S = (H+xk)/GS = RG

< p> Before introducing the principle, explain that ECC satisfies the associative law and the commutative law, that is to say, A+B+C = A+C+B = (A+C)+B.

Here is an example on WIKI to illustrate how to generate a shared secret key. You can also refer to the example of Alice And Bob.

For Alice and Bob to communicate, both parties must have public and private keys generated by ECC based on the same parameter system. So there is a common base point G for ECC.

Secret key generation stage:

Alice uses the public key algorithm KA = ka * G, generates the public key KA and the private key ka, and makes the public key KA public.

Bob uses the public key algorithm KB = kb * G, generates the public key KB and the private key kb, and makes the public key KB public.

Calculation ECDH stage:

Alice uses the calculation formula Q = ka * KB to calculate a secret key Q.

Bob uses the calculation formula Q' = kb * KA to calculate a secret key Q'.

Shared key verification:

Q = ka KB = ka * kb * G = ka * G * kb = KA * kb = kb * KA = Q'

Therefore, the shared secret keys calculated by both parties do not need to be disclosed before they can be encrypted using Q. We call Q the shared secret key.

In Ethereum, the ECIECOther contents in the encryption suite:

1. The HASH algorithm uses the most secure SHA3 algorithm Keccak.

2. The signature algorithm uses ECDSA

3. The authentication method uses H-MAC

4. The ECC parameter system uses secp256k1, others The parameter system can be found here

The whole process of H-MAC is called Hash-based Message Authentication Code. Its model is as follows:

In Ethereum's UDP communication (RPC communication encryption methods are different), then The above implementation method is adopted and extended.

First of all, the structure of Ethereum's UDP communication is as follows:

Among them, sig is the signature information encrypted by the private key. mac can be understood as a summary of the entire message, ptype is the event type of the message, and data is the RLP-encoded transmission data.

The entire encryption, authentication, and signature model of UDP is as follows:

F. What technology is used in the blockchain to achieve this function

Blockchain application The following technologies are used to achieve
The first is the consensus mechanism. Commonly used consensus mechanisms mainly include PoW, PoS, DPoS, PBFT, PAXOS, etc. Since there is no center in the blockchain system, there needs to be a preset rule to guide the nodes of all parties to reach an agreement on data processing. All data interactions must be carried out in accordance with strict rules and consensus;
The second It is cryptography technology. Cryptography technology is one of the core technologies of blockchain. Many classic algorithms of modern cryptography are used in current blockchain applications, mainly including: hash algorithm, symmetric encryption, asymmetric encryption, digital Signature etc.
The third type is distributed storage. Blockchain is a distributed ledger on a peer-to-peer network. Each participating node will independently and completely store and write block data information. The advantages of distributed storage compared with traditional centralized storage are mainly reflected in two aspects: data information is backed up on each node to avoid data loss due to single point failure; data on each node is stored independently, effectively avoiding Malicious tampering with historical data.
Smart contracts: Smart contracts allow trusted transactions without a third party. As long as one party reaches the pre-set goals of the agreement, the contract will automatically execute the transaction. These transactions are trackable and irreversible. It has the advantages of transparency, credibility, automatic execution, and mandatory performance. Blockchain technology has many uniquefeatures that make it a unique invention and give it unlimited horizons to explore.

G. Is HNB’s signature algorithm helpful to blockchain users?

Digital signature is a digital string that can only be generated by the sender of the message and cannot be forged by others. This The digital string is also an effective proof of the authenticity of the information sent by the sender of the information.
In terms of digital signatures, HNB is among the best in the industry. He uses the Secp256k1 elliptic curve, which is a parameter of the ECDSA (Elliptic Curve Digital Signature Algorithm) curve used in Bitcoin and defined in the Efficient Cryptography Standard. HNB's digital algorithm takes up very little bandwidth and storage resources, and the length of the key is very short. All users can use the same operations to complete domain operations. It is these two points that determine that HNB's signature algorithm can help blockchain users obtain digital currency content faster and more conveniently.

H. The cryptographic technology of blockchain includes

Cryptographic technology is the core of blockchain technology. The cryptographic technology of blockchain includes digital signature algorithm and hash algorithm.
Digital Signature Algorithm
Digital signature algorithm is a subset of the digital signature standard, representing a specific public key algorithm used only for digital signatures. The key is run on the message hash generated by SHA-1: to verify a signature, the hash of the message is recalculated, the signature is decrypted using the public key and the results are compared. The abbreviation is DSA.

Digital signature is a special form of electronic signature. So far, at least more than 20 countries have passed laws recognizing electronic signatures, including the European Union and the United States. my country's electronic signature law was adopted at the 11th meeting of the Standing Committee of the 10th National People's Congress on August 28, 2004. . A digital signature is defined in the ISO 7498-2 standard as: “Some data appended to a data unit, or a cryptographic transformation made to the data unit, which allows the recipient of the data unit to confirm the source and origin of the data unit. The integrity of the data unit and protects the data from forgery by a person (e.g. the recipient)”. The digital signature mechanism provides an identification method to solve problems such as forgery, denial, impersonation and tampering. It uses data encryption technology and data transformation technology to enable both parties to send and receive data to meet two conditions: the receiver can identify what the sender claims. Identity; the sender cannot later deny that it sent the data.
Digital signature is an important branch of cryptography theory. It is proposed to sign electronic documents to replace handwritten signatures on traditional paper documents, so it must have 5 characteristics.
(1) The signature is credible.
(2) The signature cannot be forged.
(3) Signatures are not reusable.
(4) Signed documents are immutable.
(5) SignThe name cannot be denied.
Hash algorithm
Hash is to convert an input of any length (also called pre-mapping, pre-image) into a fixed-length output through a hash algorithm, and the output is a hash value. This transformation is a compressed mapping in which the space of hash values ​​is usually much smaller than the space of inputs. Different inputs may hash to the same output, but the input values ​​cannot be deduced in reverse. Simply put, it is a function that compresses a message of any length into a message digest of a fixed length.
Hash algorithm is a one-way cryptographic system, that is, it is an irreversible mapping from plaintext to ciphertext, with only encryption process and no decryption process. At the same time, the hash function can change an input of any length to obtain a fixed-length output. The one-way characteristics of the hash function and the fixed length of the output data allow it to generate messages or data.
Represented by the Bitcoin blockchain, secondary hashing is used many times in the workload proof and key encoding process, such as SHA (SHA256(k)) or RIPEMD160 (SHA256(K)). This The advantage of this method is that it increases the workload or increases the difficulty of cracking if the protocol is not clear.
Represented by the Bitcoin blockchain, the two main hash functions used are:
1. SHA-256, mainly used to complete PoW (proof of work) calculations;
2.RIPEMD160, mainly used to generate Bitcoin addresses. As shown in Figure 1 below, the process of generating an address from a public key for Bitcoin.