Write complete cryptographic primitives specification

[XiaoSaGe99]

Summary

This PR expands specs/crypto.md from basic parameter tables into a complete formal specification of the five AnonVote cryptographic primitives, covering security properties, failure modes, implementation references, and supporting documentation.

Changes

Per-primitive sections (5 primitives)

Each primitive now includes:

• Algorithm and parameters (existing tables preserved)
• Security property — formal description of the cryptographic guarantee (e.g., preimage resistance, IND-CCA2, unpredictability)
• Failure modes table — each failure mode with consequence and severity rating (Critical/High/Medium/Low)
• Implementation reference — annotated code snippet from AnonVote/js — src/crypto.ts

New sections

• Dependency diagram — ASCII flow chart showing how the five primitives compose into the full vote lifecycle (eligibility → token issuance → vote casting → tallying)
• Primitive dependency table — maps each primitive to its dependencies and caller
• Key management — generation, storage, lifecycle stages, rotation procedure
• Threat model — honest documentation of what is protected (6 items) and what is NOT protected (6 items, with recommended mitigations)

Design rationale notes

• GCM vs CBC comparison table with explanation of why GCM was chosen
• Why hashToken deliberately omits normalization (unlike hashIdentifier)
• Why decryptVote must throw on auth tag failure rather than returning silently

Acceptance criteria met

• specs/crypto.md covers all five primitives with algorithm, input/output format, security property, and failure modes
• Key management section is included
• Dependency diagram shows how primitives compose
• Threat model honestly covers what is and is not protected
• A technical reviewer who has not read any other AnonVote repo can understand the full crypto layer from this document alone

Closes #1

[Just-Bamford]

@XiaoSaGe99 you know i didnt assign you to this issue right ? even if i merge this youre not getting the points

I can see your application on my dashboard so i dont know how to assign you

[XiaoSaGe99]

Hi @Just-Bamford, thanks for the heads-up! I wasn't aware of the GrantFox workflow. Could you let me know how I can be properly assigned? I'm happy to follow whatever process you need — whether that's me claiming the issue through the GrantFox dashboard, or whatever works on your end. Please let me know and I'll take care of it right away.

[Just-Bamford]

@XiaoSaGe99 I can see your application on the contributors app but I can't see it on my maintainer dashboard, I don't know its thats a bug or what. Maybe try applying to other issues on my repo