A digital signature is a digital string, which can only be generated by the sender of the information, and others cannot forge it. This number string is also an effective proof of the authenticity of the information sent by the information sender.

Digital signature is the application of asymmetric key encryption technology and digital digest technology.

The integrity of the digital signature document is easy to verify (no need for printing, signing or handwriting experts), and the digital signature is undeniable (no need for handwriting experts to verify).

Simply put, the so-called digital signature is some data attached to the data unit, or the cryptographic transformation of the data unit. This kind of data or transformation allows the receiver of the data unit to confirm the source and integrity of the data unit, and protects the data from being forged by people (such as the receiver). This is a method of signing an electronic message, and the signed message can be transmitted in a communication network. Digital signature can be obtained based on both public key cryptosystem and private key cryptosystem. At present, digital signature is mainly based on public key cryptosystem. Include general digital signature and special digital signature. Common digital signature algorithms are RSA and so on.

So explain your question in one sentence: the main reason is that RSA has the characteristics of public key and private key.