The file bbs_signature.c contains a test program to compute a BBS
signature as described in the paper "Revisiting BBS Signatures"
using the library of subroutines developed in the book Elliptic
Cruve Cryptography for Developers (http://mng.bz/NVev)

The basic idea is to compute the hash of multiple messages, called
variable l in the paper. Here I use the value NUMESG = 16. A vector
of points is used to multiply the hash of each message. As stated in
the paper, a fixed method can be used to create these points based
on the index for each point. The subroutine msgpoint() performs that
task.

Note that in a real situation the values output from msgpoint() will
be used by both the signer and verifier. So the code used to create
point Csum will be used every time the signature is verified.

For details on how the library works, see the book Elliptic Curve
Cryptography for Developers.

Here is the reference to the paper:

@misc{cryptoeprint:2023/275,
      author = {Stefano Tessaro and Chenzhi Zhu},
      title = {Revisiting BBS Signatures},
      howpublished = {Cryptology ePrint Archive, Paper 2023/275},
      year = {2023},
      note = {\url{https://eprint.iacr.org/2023/275}},
      url = {https://eprint.iacr.org/2023/275}
}