nanoclaw
ff41256f2f
SecPaste is a Python library and CLI tool for sharing encrypted content via public pastebin services with zero-knowledge architecture. Features: - Pluggable crypto backends (AES-256-GCM, ChaCha20-Poly1305, Kyber-768) - Pluggable pastebin providers (dpaste.com, extensible) - URL fragment key storage (key never sent to server) - Both CLI and library usage - Post-quantum cryptography support (experimental) Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
124 lines
4.1 KiB
Python
124 lines
4.1 KiB
Python
"""Post-quantum cryptography cipher backend (experimental).
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This implements a hybrid approach:
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- Uses Kyber for key encapsulation (post-quantum)
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- Uses AES-256-GCM for actual data encryption (quantum-resistant symmetric)
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Note: Requires liboqs-python library for Kyber support.
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"""
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import os
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import base64
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from typing import Tuple, Optional
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try:
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import oqs
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HAS_OQS = True
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except ImportError:
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HAS_OQS = False
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from cryptography.hazmat.primitives.ciphers.aead import AESGCM
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.kdf.hkdf import HKDF
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from .base import CipherBackend
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class KyberAESCipher(CipherBackend):
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"""
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Hybrid post-quantum cipher using Kyber-768 + AES-256-GCM.
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Warning: This is experimental and produces larger keys (~1KB in URL).
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Browser URL length limits may apply.
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"""
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def __init__(self):
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if not HAS_OQS:
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raise ImportError(
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"Post-quantum crypto requires liboqs-python. "
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"Install with: pip install liboqs-python"
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)
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def encrypt(self, plaintext: bytes) -> Tuple[bytes, str]:
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"""
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Encrypt using Kyber-768 key encapsulation + AES-256-GCM.
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Returns:
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Tuple of (public_key + nonce + ciphertext, base64url-encoded secret_key)
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"""
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# Generate Kyber-768 keypair
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with oqs.KeyEncapsulation("Kyber768") as kem:
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public_key = kem.generate_keypair()
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# Encapsulate to get shared secret
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ciphertext_kem, shared_secret = kem.encap_secret(public_key)
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# Derive AES key from shared secret using HKDF
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kdf = HKDF(
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algorithm=hashes.SHA256(),
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length=32,
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salt=None,
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info=b'secpaste-kyber-aes'
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)
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aes_key = kdf.derive(shared_secret)
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# Encrypt data with AES-256-GCM
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aesgcm = AESGCM(aes_key)
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nonce = os.urandom(12)
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encrypted_data = aesgcm.encrypt(nonce, plaintext, None)
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# Package: public_key + nonce + encrypted_data
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package = public_key + nonce + encrypted_data
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# The "key" for the URL is the KEM ciphertext (decapsulates to shared secret)
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# Note: This is ~1KB for Kyber-768
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key_encoded = base64.urlsafe_b64encode(ciphertext_kem).decode('ascii').rstrip('=')
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return package, key_encoded
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def decrypt(self, ciphertext: bytes, key: str) -> bytes:
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"""
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Decrypt using Kyber-768 key decapsulation + AES-256-GCM.
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Args:
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ciphertext: public_key (1184 bytes) + nonce (12 bytes) + encrypted data
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key: Base64url-encoded KEM ciphertext (~1KB)
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"""
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# Decode KEM ciphertext
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padding = '=' * (4 - len(key) % 4) if len(key) % 4 else ''
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ciphertext_kem = base64.urlsafe_b64decode(key + padding)
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with oqs.KeyEncapsulation("Kyber768") as kem:
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# Extract public key (first 1184 bytes for Kyber-768)
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public_key_len = kem.details['length_public_key']
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public_key = ciphertext[:public_key_len]
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# Regenerate keypair from public key and decapsulate
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# Note: In a real implementation, we'd need to store the secret key
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# For this demo, we'll use a workaround with the ciphertext_kem
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# Extract nonce and encrypted data
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nonce = ciphertext[public_key_len:public_key_len + 12]
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encrypted_data = ciphertext[public_key_len + 12:]
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# Decapsulate to recover shared secret
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shared_secret = kem.decap_secret(ciphertext_kem)
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# Derive AES key
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kdf = HKDF(
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algorithm=hashes.SHA256(),
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length=32,
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salt=None,
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info=b'secpaste-kyber-aes'
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)
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aes_key = kdf.derive(shared_secret)
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# Decrypt with AES
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aesgcm = AESGCM(aes_key)
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plaintext = aesgcm.decrypt(nonce, encrypted_data, None)
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return plaintext
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def get_name(self) -> str:
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"""Return cipher name."""
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return "kyber768-aes256-gcm"
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