Mesmerizing Chameleon Signatures
14 May 2020This is a mirror of my post at https://medium.com/@stevenyue/mesmerizing-chameleon-signatures-4cdb3c8ab1c3.
For the past year, I having been taking classes at Stanford under Professor Dan Boneh and learning about different topics in the field of Cryptography. It has truly become an amazing journey. There are so many marvelous ideas in this field and a lot of them essentially reshaped the world.
Therefore I decided to start writing about what I have learned in a series of posts. This first post is actually a summary of an old paper that I recently read.
Preface
Signature schemes are essential to our daily lives. Before computers have existed, we have been signing off papers and documents with our names for a long time. A proper signature simply represents identity and authenticity. Digital Signature is essentially the same idea but in the world of computers. A signature proves the validity of what we say.
Aside from signatures, there’s also this idea of a Commitment scheme. A hash function is a commitment scheme, as long as it’s hard to produce collisions. Similar to signatures, a commitment proves that we are “committed” to some value. But on the other hand, it also hides the value of it. A valid commitment scheme should satisfy two properties:
- Binding: A commitment can only bind to one value. It’s impossible to produce another value that also aliases to the same commitment.
- Hiding: A commitment should hide its committed value. By just looking at the commitment itself, the observer should have no way to regain knowledge of the committed value.
Signatures and commitments are equally important in our digital lives. Today I want to talk about a special kind of signatures that leverages a beautiful commitment scheme — Chameleon Signatures.