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2026-09-14 23:22:10 +09:00
commit 9f9c8fb69b
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+from Crypto.Cipher import ChaCha20_Poly1305
+from .._rfc7516.registry import JWERegistry
+from .._rfc7516.models import JWEEncModel
+
+__all__ = ["ChaCha20EncModel", "JWE_ENC_MODELS", "register_chacha20_poly1305"]
+
+
+class ChaCha20EncModel(JWEEncModel):
+    # https://datatracker.ietf.org/doc/html/draft-amringer-jose-chacha-02#section-4
+    cek_size = 256
+    recommended = False
+
+    def __init__(self, name: str, description: str, iv_size: int):
+        self.name = name
+        self.description = description
+        self.iv_size = iv_size
+
+    def encrypt(self, plaintext: bytes, cek: bytes, iv: bytes, aad: bytes) -> tuple[bytes, bytes]:
+        """Key Encryption with AEAD_CHACHA20_POLY1305"""
+        chacha = ChaCha20_Poly1305.new(key=cek, nonce=iv)
+        chacha.update(aad)
+        ciphertext, tag = chacha.encrypt_and_digest(plaintext)
+        return ciphertext, tag
+
+    def decrypt(self, ciphertext: bytes, tag: bytes, cek: bytes, iv: bytes, aad: bytes) -> bytes:
+        """Key Decryption with AEAD_CHACHA20_POLY1305."""
+        chacha = ChaCha20_Poly1305.new(key=cek, nonce=iv)
+        chacha.update(aad)
+        return chacha.decrypt_and_verify(ciphertext, tag)
+
+
+C20P = ChaCha20EncModel("C20P", "ChaCha20-Poly1305", 96)
+XC20P = ChaCha20EncModel("XC20P", "XChaCha20-Poly1305", 192)
+
+JWE_ENC_MODELS = [C20P, XC20P]
+
+
+def register_chacha20_poly1305() -> None:
+    for model in JWE_ENC_MODELS:
+        JWERegistry.register(model)