Module privacy 

Loop Agent SDK - Privacy Layer

Blind indexing for card fingerprints. Loop never stores raw card IDs — only one-way cryptographic tags.

Security Model

• Pepper: System-wide secret stored in AWS Secrets Manager
• Algorithm: HMAC-SHA256
• Output: loop_fp_{hex_hash}
• Irreversible: Even with DB access, card IDs cannot be recovered

Double-Blind Vaulting

1. Webhook arrives with card_id
2. Immediately hash to loop_fp_*
3. Purge raw card_id from memory
4. All subsequent operations use only the fingerprint

This means:

• Logs never contain card IDs
• DynamoDB never sees card IDs
• Even Loop engineers cannot reverse fingerprints

Structs

LoopFingerprint

A Loop fingerprint (one-way hash of card_id)

PrivacyConfig

Privacy configuration

PrivacyLayer

Privacy layer for card fingerprint hashing

Enums

PrivacyError

Privacy layer errors

Functions

create_pepper_secret

Create the pepper secret in AWS Secrets Manager Run this during initial setup

generate_pepper

Generate a new random pepper (32 bytes) Run this once to create the initial secret