# SM-PY-BC Progress Report

## Completed Modules

### Infrastructure
- [x] Project structure and configuration
- [x] Utility classes: `Pack`, `Arrays`, `Integers`, `SecureRandom`, `BigIntegers`
- [x] Interfaces: `Memoable`, `Digest`
- [x] Exception classes: `CryptoException`, `DataLengthException`, `InvalidCipherTextException`

### SM3
- [x] `SM3Digest` implementation
- [x] Unit tests with standard vectors

### Elliptic Curve Math
- [x] `ECFieldElement` (Fp)
- [x] `ECCurve` (Fp)
- [x] `ECPoint` (Fp, Jacobian coordinates)
- [x] `ECMultiplier` (LTR Double-and-Add, FixedPointCombMultiplier placeholder)

### SM2
- [x] Parameter classes (`ECDomainParameters`, `ECKeyParameters`, etc.)
- [x] `DSAKCalculator` (Base interface)
- [x] `RandomDSAKCalculator` (Random K generation)
- [x] `DSAEncoding` (Base interface)
- [x] `StandardDSAEncoding` (ASN.1 DER encoding/decoding)
- [x] `SM2Signer` (Sign/Verify)
- [x] Unit tests for Sign/Verify (Self-consistency pass)
- [x] **`SM2Engine` (Encryption/Decryption)**
  - [x] C1C2C3 mode support
  - [x] C1C3C2 mode support
  - [x] KDF with SM3 digest
  - [x] Comprehensive unit tests (29 tests covering basic functionality, different message lengths, mode compatibility, output size, ciphertext structure, multiple key pairs, randomness, error handling, edge cases, and reusability)

### SM4
- [x] **`SM4Engine` (Block Cipher)**
  - [x] 128-bit block cipher with 128-bit key
  - [x] 32-round Feistel structure
  - [x] Encryption and decryption
  - [x] Key expansion algorithm
  - [x] S-box substitution and linear transformations
  - [x] Comprehensive unit tests (18 tests covering basic functionality, standard vectors, million-iteration tests, round-trip, boundary conditions, reusability, and offset handling)
- [x] **Cipher Modes**
  - [x] **`ECBBlockCipher` (ECB Mode)**
    - [x] Electronic Codebook mode (simplest mode, not recommended for production)
    - [x] Direct block-by-block encryption
  - [x] **`CBCBlockCipher` (CBC Mode)**
    - [x] Cipher Block Chaining mode implementation
    - [x] IV (Initialization Vector) support
    - [x] Chaining behavior for multiple blocks
    - [x] Reset functionality
    - [x] Comprehensive unit tests (12 tests)
  - [x] **`SICBlockCipher` (CTR Mode)**
    - [x] Counter (CTR) mode implementation
    - [x] Stream cipher capability
    - [x] Comprehensive unit tests (15 tests)
  - [x] **`OFBBlockCipher` (OFB Mode)**
    - [x] Output Feedback mode implementation
    - [x] Configurable feedback block size
    - [x] Comprehensive unit tests (16 tests)
  - [x] **`CFBBlockCipher` (CFB Mode)**
    - [x] Cipher Feedback mode implementation
    - [x] Self-synchronizing stream cipher
    - [x] Comprehensive unit tests (17 tests)
  - [x] **`GCMBlockCipher` (GCM Mode - AEAD)**
    - [x] Galois/Counter Mode authenticated encryption
    - [x] AEAD support with AAD processing
    - [x] Authentication tag generation/verification
    - [x] Supporting classes: `AEADParameters`, `GCMUtil`
- [x] **`SM4` High-Level API**
  - [x] Convenient encrypt/decrypt interface
  - [x] Key generation
  - [x] Block-level and message-level operations
  - [x] Built-in PKCS7 padding

### Padding Schemes

- [x] **`PKCS7Padding`**
  - [x] PKCS#7 padding implementation (RFC 5652)
  - [x] Add and remove padding
  - [x] Padding validation
  - [x] Supports block sizes 1-255 bytes
  - [x] Comprehensive unit tests (19 tests covering padding/unpadding, validation, round-trip, edge cases, and integration with CBC mode)
- [x] **`ZeroBytePadding`**
  - [x] Zero byte padding (simplest scheme)
  - [x] Warning: Cannot reliably remove if data ends with zeros
  - [x] Use for legacy compatibility
- [x] **`ISO10126Padding`**
  - [x] ISO 10126 padding (random bytes + length)
  - [x] Withdrawn standard but still in use
  - [x] Add and remove with validation
- [x] **`ISO7816d4Padding`**
  - [x] ISO/IEC 7816-4 padding (smart card standard)
  - [x] 0x80 marker followed by zeros
  - [x] Unambiguous and reliable
  - [x] Comprehensive tests (21 tests covering all schemes, comparisons, and edge cases)

## Known Issues
- `SM2Signer` standard test vector from GM/T 0003-2012 fails on public key derivation check. However, self-generated key pairs work correctly for signing and verification. This suggests a potential mismatch in the test vector constants setup rather than the core logic.

### SM2 Key Exchange
- [x] **`SM2KeyExchange` (Key Agreement Protocol)**
  - [x] Key agreement between two parties
  - [x] Initiator and responder roles
  - [x] User ID support via `ParametersWithID`
  - [x] KDF (Key Derivation Function) implementation
  - [x] Confirmation tag generation (S1/S2)
  - [x] Z value computation (user identification hash)
  - [x] Variable-length key output
  - [x] Memoable optimization for KDF
  - [x] Supporting classes:
    - [x] `SM2KeyExchangePrivateParameters`
    - [x] `SM2KeyExchangePublicParameters`
    - [x] `ECAlgorithms` utility
    - [x] `FixedPointCombMultiplier`
  - [x] Comprehensive unit tests (14 tests covering basic key exchange, both parties producing same key, confirmation protocol, parameter validation, different key lengths, error handling, empty user IDs, and different user IDs producing different keys)

### High-Level API
- [x] **`SM2` (High-Level Convenience API)**
  - [x] Key pair generation
  - [x] Encryption/Decryption with flexible parameter formats
  - [x] Signing/Verification with flexible parameter formats
  - [x] Parameter access and validation
  - [x] Comprehensive unit tests (19 tests covering key generation, encryption, decryption, signing, verification, parameter validation, different message formats, multiple operations, and edge cases)

## Next Steps
1. ~~Implement `SM2Engine` for encryption/decryption.~~ ✅ **COMPLETED**
2. ~~Implement `SM4` block cipher.~~ ✅ **COMPLETED**
3. ~~Implement CBC cipher mode.~~ ✅ **COMPLETED**
4. ~~Implement CTR/SIC mode.~~ ✅ **COMPLETED**
5. ~~Implement OFB mode.~~ ✅ **COMPLETED**
6. ~~Implement CFB mode.~~ ✅ **COMPLETED**
7. ~~Implement PKCS#7 padding.~~ ✅ **COMPLETED**
8. ~~Implement additional padding schemes.~~ ✅ **COMPLETED**
9. ~~Implement `SM2KeyExchange`.~~ ✅ **COMPLETED**
10. ~~Implement GCM mode (authenticated encryption).~~ ✅ **COMPLETED**
11. ~~Implement SM2 high-level API.~~ ✅ **COMPLETED**
12. Add comprehensive unit tests for GCM mode
13. Create comprehensive examples and documentation
14. Package and publish to PyPI
