ENCRYPTION_SERVICE

AES-256-CTR encryption/decryption utilities with deterministic IV generation for cross-language interoperability.

Installation

pip install ENCRYPTION_SERVICE

Quick Start

Set environment variables in .env

ENCRYPTION_KEY=your-secret-phrase   # MUST be ≥ 32 bytes, cryptographically random

Import and use

from ENCRYPTION_SERVICE import Aes256CtrEncryption

# Encrypt plaintext to base64
token = Aes256CtrEncryption.encrypt("s3cr3t")   # → "XXXXX..."

# Decrypt back to plaintext
plain = Aes256CtrEncryption.decrypt(token)      # → "s3cr3t"

# Decrypt a nested field in JSON
payload = {"db": {"pass": Aes256CtrEncryption.encrypt("hunter2")}}
pw = Aes256CtrEncryption.decrypt_json_field(payload, "db.pass")  # → "hunter2"

⚠️ SECURITY: ENCRYPTION_KEY must be ≥ 32 bytes of cryptographically random data. Never use a human-chosen password. A warning fires on first use if key is too short.

Configuration

Environment Variables

API Reference

Aes256CtrEncryption.encrypt(plaintext: str) -> str

Encrypts arbitrary plaintext to a base64 string.

• plaintext: String to encrypt
• Returns: Base64-encoded ciphertext

Aes256CtrEncryption.decrypt(encoded_ciphertext: str) -> str

Decrypts base64-encoded ciphertext back to plaintext.

• encoded_ciphertext: Base64-encoded ciphertext from encrypt()
• Returns: Original plaintext string
• Raises: ValueError if ciphertext is malformed (shorter than 16 bytes)

Aes256CtrEncryption.decrypt_json_field(encrypted_json: dict, json_path: str) -> str

Decrypts a single nested field in a JSON object.

• encrypted_json: Dictionary containing encrypted fields
• json_path: Dot-notation path (e.g. "user.credentials.password")
• Returns: Decrypted plaintext string
• Raises: ValueError if path doesn't exist or points to non-string

Key Features

1. Deterministic IV Generation — Same plaintext always produces same ciphertext (cross-language compatible)
2. AES-256-CTR Mode — High-performance encryption with no padding issues
3. SHA-256 Key Derivation — Compatible with Rust sibling implementation
4. Retry with Exponential Backoff + Jitter — 3 attempts with exponential backoff and ±25% jitter
5. Lazy Config Loading — No side effects on import; validated on first use
6. Pure Cryptographic Functions — No side effects, thread-safe, deterministic

Security Notes

• Key Requirements: Use cryptographically random keys ≥ 32 bytes. SHA-256 derivation provides no brute-force resistance.
• Deterministic Encryption: Identical plaintexts produce identical ciphertexts — acceptable for this use case.
• Cross-Language Interop: IV derivation matches Rust implementation exactly.

Performance

┌──────────────────────┬──────────┬──────────┬─────────────┬──────────┬──────────┐
│ Test                 │ Ops      │ Time     │ Throughput  │ Target   │ Status   │
├──────────────────────┼──────────┼──────────┼─────────────┼──────────┼──────────┤
│ Encrypt (1-thread)   │  1,000   │ 0.038 s  │ 26,253/sec  │ 10k/sec  │ ✅ PASS  │
│ Decrypt (1-thread)   │  1,000   │ 0.028 s  │ 35,920/sec  │ 10k/sec  │ ✅ PASS  │
│ Round-trip           │    100   │ 0.058 ms │    avg/call │  < 1 ms  │ ✅ PASS  │
│ JSON field decrypt   │    500   │ 0.014 s  │ 37,171/sec  │ 10k/sec  │ ✅ PASS  │
│ Encrypt (4-thread)   │  1,000   │ 0.092 s  │ 11,052/sec  │ 10k/sec  │ ✅ PASS  │
│ Encrypt (8-thread)   │  2,000   │ 0.197 s  │ 10,163/sec  │ 10k/sec  │ ✅ PASS  │
└──────────────────────┴──────────┴──────────┴─────────────┴──────────┴──────────┘
System: Ubuntu 24.04.4 LTS | AMD Ryzen 7 5800H (16 cores, 13Gi RAM) | Python 3.12.3
Tested: 2026-04-03 16:56 UTC

GIL note: Multi-thread throughput is limited by Python's GIL — AES-CTR is CPU-bound. Use multiprocessing if CPU-bound parallelism is required.

Error Handling

The library will raise ValueError if:

• ENCRYPTION_KEY is not set (raised on first crypto call, not at import)
• Ciphertext is shorter than 16 bytes (truncated IV)
• JSON path does not exist in the provided dict
• JSON path resolves to a non-string leaf (not an encrypted value)

UserWarning fires on first use if ENCRYPTION_KEY is shorter than 32 bytes.

Retry Policy

All cryptographic operations use @with_retry decorator:

• Max attempts: 3
• Delay: Exponential backoff (1s, 2s, 4s) with ±25% jitter
• Retryable: All exceptions (local crypto has no 4xx-equivalent)
• Logging: WARNING per attempt, ERROR on exhaustion

Test Coverage

python3 -m pytest ENCRYPTION_SERVICE.py -v