Add folder anatomy (scripts/agent.py + references/api-reference.md) for 648 cybersecurity skills

Complete skill folder anatomy across all cybersecurity skills:
- scripts/agent.py: 80-150 line Python agents using real libraries (impacket,
  boto3, azure-mgmt-*, kubernetes, pefile, yara, scapy, shodan, stix2, etc.)
- references/api-reference.md: real API documentation with method signatures
- LICENSE: MIT license for all skill folders

skills/implementing-zero-knowledge-proof-for-authentication/references/api-reference.md

@@ -0,0 +1,50 @@
+# API Reference: Zero-Knowledge Proof Authentication
+
+## hashlib (Python Standard Library)
+
+### PBKDF2 Key Derivation
+```python
+import hashlib
+key = hashlib.pbkdf2_hmac("sha256", password.encode(), salt.encode(), iterations)
+```
+
+### SHA-256 Hashing (Fiat-Shamir Heuristic)
+```python
+challenge = int(hashlib.sha256(data.encode()).hexdigest(), 16) % prime
+```
+
+## secrets (Python Standard Library)
+
+| Function | Description |
+|----------|-------------|
+| `secrets.randbelow(n)` | Cryptographically secure random int in [0, n) |
+| `secrets.token_hex(n)` | Random hex string of n bytes |
+| `secrets.token_bytes(n)` | Random bytes of length n |
+
+## Schnorr Protocol Steps
+
+| Step | Prover | Verifier |
+|------|--------|----------|
+| Setup | Private key x, public key y=g^x mod p | Knows g, p, y |
+| Commit | Pick random k, send r=g^k mod p | Receive r |
+| Challenge | - | Send random c |
+| Response | Send s = k - c*x mod (p-1) | Check g^s * y^c == r mod p |
+
+## Fiat-Shamir Heuristic (Non-Interactive)
+```
+c = H(g || r || y)   # Challenge derived from hash
+s = k - c * x mod (p-1)
+```
+
+## ZKP Properties
+| Property | Guarantee |
+|----------|-----------|
+| Completeness | Honest prover always convinces verifier |
+| Soundness | Dishonest prover fails with high probability |
+| Zero-Knowledge | Verifier learns nothing beyond validity |
+
+## References
+- Schnorr Protocol: https://en.wikipedia.org/wiki/Schnorr_identification
+- RFC 8235 (Schnorr NIZK): https://www.rfc-editor.org/rfc/rfc8235
+- hashlib docs: https://docs.python.org/3/library/hashlib.html
+- secrets docs: https://docs.python.org/3/library/secrets.html