plus/minus epsilon

Certificate Transparency (CT) is a relatively new addition to the TLS ecosystem. Its fundamental goal is to provide the tools for website operators to detect the mis-issuance of certificates for their own websites. Historically, this is something that only large tech companies have been able to do successfully.

In Adi Shamir's paper titled How to Share a Secret, he quotes this problem from a combinatorics textbook:

Eleven scientists are working on a secret project. They wish to lock up the documents in a cabinet so that the cabinet can be opened if and only if six or more of the scientists are present. What is the smallest number of locks needed? What is the smallest number of keys to the locks each scientist must carry?

I've decided to start writing a regular series of short blog posts about crypto. The focus will be more on the social and problem-solving aspects of crypto rather than the math.

I've realized that some design choices in my bn256 implementation don't seem well-motivated to everybody... including myself. So I'd like to document here all of the tricks I find myself forgetting.

In short:

1. Because small functions have their runtime dominated by function-call overhead.
2. Because data is stored on the heap unnecessarily.
3. Because you can't take advantage of the featurefulness of assembly.

White-Box Cryptography is the study of securing symmetric encryption algorithms in the white-box attack context (WBAC), where an adversary obtains an implementation of the algorithm and is allowed to observe/alter every step of its execution (with instantiated cryptographic keys).

We know that a data structure is a particular way of organizing data so that we can efficiently solve a problem with it. Perhaps a cryptographic data structure would just be the same thing, but with a notion of security determined by an adversary's ability to win a certain game.

In a sense, they're minimal cryptosystems that can be glued together into more complex cryptosystems similar to the way that fundamental data structures can be glued together to give solutions to increasingly complicated problems.