Getting started with blockchain | Multi-signature is safe but not private enough? Ring signature and blind signature

As we all know, the blockchain is a distributed ledger . For the book, its privacy is extremely important. Therefore, discovering some technologies to ensure its security has become the research direction of many people. Signature technology is one of them, and different signatures bring different security, such as Multi-signature, group signature, etc. Let us talk about the ring signature and blind signature in digital signature technology today.

01 ring signature

The ring signature, literally means the signature that surrounds it, in fact, this is not without reason.

According to legend, the idea of ​​ring signatures originated in France in the seventeenth century. At that time, the French Minister wanted to give the King a sigh, but he did not want the King to know who was the leader. He took a circular signature. The signature was surrounded by a circle, and the name was not in order. The leader was unknown. .

The word Ring Signature was proposed by the three cryptographers Rivest, Shamir and Tauman in 2001. It is a digital signature scheme and a simplified group signature. In the ring signature, only the ring members are not. Managers do not need cooperation between ring members .

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The process of ring signature is as follows: 1. key generation; 2. signature; 3. signature verification. Using asymmetric encryption technology, private key encryption (signature), public key decryption, and thus can certainly determine the name of the person who has the private key.

A popular example is:

The first step: key generation. In a shared apartment, each person has a different gate password (public key), and each has its own bedroom door key (private key);

The second step: signature confirmation . The cleaning aunt came to clean every week. The landlord asked each tenant to receive her when the cleaning aunt cleaned every week, but the tenant did not want the landlord to know who opened the door every time. When aunt wants to come in, he can only provide one public key through one of the tenants.

Aunt can only open the door through the public key of a tenant every time, but because the aunt does not have a private key, he can't enter the door of each tenant, and he doesn't know who's used the public key. (The landlord can use the aunt according to whether You can enter the door to know that the tenant opened the door to the aunt, that is, the signature confirmation).

The third step : signature verification . The landlord can know that the tenant opened the door to the aunt according to the aunt who can enter the door and whether it has been cleaned, but I don’t know which tenant.

Ring signatures do not require managers, and because of their unconditional anonymity and unforgeability , they are more prominent in terms of privacy than general group signatures. Among the many digital currencies, Monroe is using the technology of ring signature and is recognized as one of the best privacy cryptocurrencies .

02 blind signature

Like a ring signature, blind signature is a special digital signature technique. The blind signature is known for the fact that the signature person does not see the specific content of the signed document. It has two notable features: one is that the signer is invisible to the content of the message; the other is that the signature cannot be tracked after the signature is published. Signature .

In 1983, David Chaum proposed blind signatures primarily to achieve unlinkability. Someone uses a very vivid example to describe blind signatures:

First put the hidden file into the envelope. No one can read it. Signing the document is by placing a copy of the paper in the envelope. When the signer signs the envelope, his signature is signed on the paper through the carbon paper.

In this way, the signer does not see the content of the signature, and even if the signature is made public, the signer cannot know which signature the signature was.

Some people will think that the signer can't see the signature content. Who is willing to sign it? What application scenarios are there?

For example, when you buy things everyday, cash expenses are difficult for others to track; but when you transfer money online, it is easy for third parties (such as banks) to check their consumption. The role of blind signature is to Don't let the bank know where your money is going.

The most important thing in the blind signature operation process is the blinding technique. The data of the signer is presented after being blinded. After the signature and after blinding, the signer cannot be reminded of the previous blinded data. .

03 Summary

The untrackability of ring signatures and blind signatures is a major breakthrough in signature technology, but it also gives criminals the opportunity to continue to improve their functions, such as blind signatures and the emergence of fair blind signatures.

With the development of digital currency, digital signature technology has also become an important and urgent research direction. What kind of signature technology can better protect the privacy of our digital assets is still being explored.

Do you still know or understand what digital signature technology? Feel free to leave your opinion in the comments section.

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Author | Sanli

Produced|Baihua blockchain (ID: hellobtc)

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