How to do an electronic signature?

How to do an electronic signature?

Before introducing the electronic signature, we will first introduce Hash, also known as Hash or Hash.

The Hash function is defined as a variable-length input to a fixed-length output.

Common Hash algorithms: MD5 (128 bits), regardless of the length of the input, will become a fixed length of 128 bits output.

Hash features:

1. variability: even if the original information changes by 1 bit, the Hash output will have unpredictable huge changes.

2. irreversible: It is impossible or extremely difficult to construct a satisfying input information through the Hash result.

In the text of symmetric encryption and asymmetric encryption, we have learned that in asymmetric encryption, public keys are used for encryption and then private keys are used for decryption.

In electronic signatures, another feature is that private keys are used for encryption, and public keys are used for decryption. For example:

Let's first think about the nature of signatures in real life:

1. It is undeniable that the font you sign cannot be imitated by others.

2. The integrity of the signed documents cannot be modified.

Let's look at the electronic signature:

If you directly encrypt the original message using the private key, this method is not recommended because asymmetric encryption is slow.

We first use the Hash value of the original information, and then use the private key signature for the Hash value. Then, send the original information and signature information together to the Target, which is equivalent to sending the signed file and signature together to the Target.

Target first decrypts the signature information using the public key, and then calculates the Hash value of the original information. The Hash value is compared with the Hash value decrypted by the public key. If it is consistent, the signature is not tampered.

Electronic signatures also have the following characteristics:

1. Non-Repudiation: Use the private key for signature. The private key is only available to you, and others cannot have your private key.

2. Integrity: Hash Value Verification ensures integrity because it is variable and irreversible.

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