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>
66 lines
1.9 KiB
Python
66 lines
1.9 KiB
Python
"""ChaCha20-Poly1305 cipher backend."""
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import os
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import base64
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from typing import Tuple
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from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
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from .base import CipherBackend
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class ChaCha20Cipher(CipherBackend):
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"""ChaCha20-Poly1305 authenticated encryption."""
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def encrypt(self, plaintext: bytes) -> Tuple[bytes, str]:
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"""
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Encrypt using ChaCha20-Poly1305.
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Returns:
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Tuple of (nonce + ciphertext, base64url-encoded key)
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"""
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# Generate random 256-bit key
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key = ChaCha20Poly1305.generate_key()
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chacha = ChaCha20Poly1305(key)
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# Generate random 96-bit nonce
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nonce = os.urandom(12)
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# Encrypt and authenticate
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ciphertext = chacha.encrypt(nonce, plaintext, None)
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# Prepend nonce to ciphertext
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encrypted_data = nonce + ciphertext
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# Encode key for URL fragment
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key_encoded = base64.urlsafe_b64encode(key).decode('ascii').rstrip('=')
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return encrypted_data, key_encoded
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def decrypt(self, ciphertext: bytes, key: str) -> bytes:
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"""
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Decrypt using ChaCha20-Poly1305.
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Args:
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ciphertext: Nonce (12 bytes) + encrypted data
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key: Base64url-encoded 256-bit key
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"""
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# Decode key (add padding if needed)
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padding = '=' * (4 - len(key) % 4) if len(key) % 4 else ''
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key_bytes = base64.urlsafe_b64decode(key + padding)
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if len(key_bytes) != 32:
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raise ValueError("Invalid key length. Expected 32 bytes for ChaCha20.")
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# Extract nonce and ciphertext
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nonce = ciphertext[:12]
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encrypted = ciphertext[12:]
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# Decrypt
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chacha = ChaCha20Poly1305(key_bytes)
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plaintext = chacha.decrypt(nonce, encrypted, 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 "chacha20-poly1305"
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