py 把明文值分段RSA加密

好的，您可以使用Python的`cryptography`库来实现RSA加密。首先，您需要生成RSA密钥对：

from cryptography.hazmat.primitives.asymmetric import rsa, padding
from cryptography.hazmat.primitives import serialization

# 生成密钥对
private_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048
)
public_key = private_key.public_key()

# 保存密钥对到文件
with open('private_key.pem', 'wb') as f:
    f.write(private_key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.PKCS8,
        encryption_algorithm=serialization.NoEncryption()
    ))
with open('public_key.pem', 'wb') as f:
    f.write(public_key.public_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PublicFormat.SubjectPublicKeyInfo
    ))

接下来，您可以使用公钥对明文进行加密：

from cryptography.hazmat.primitives.asymmetric import padding

# 加载公钥
with open('public_key.pem', 'rb') as f:
    public_key = serialization.load_pem_public_key(
        f.read(),
        backend=default_backend()
    )

# 分段加密
plaintext = b'Hello, world!'
chunk_size = 190  # 2048 bit key size / 8 - 2 * hash size
ciphertext = b''
for i in range(0, len(plaintext), chunk_size):
    chunk = plaintext[i:i+chunk_size]
    ciphertext += public_key.encrypt(
        chunk,
        padding.OAEP(
            mgf=padding.MGF1(algorithm=hashes.SHA256()),
            algorithm=hashes.SHA256(),
            label=None
        )
    )

print(ciphertext)

在此示例中，我们将明文分成大小为190字节的块，并使用OAEP填充方案进行加密。在加密过程中，我们使用公钥对每个块进行加密，并将所有密文块连接在一起形成最终的密文。