长时效性数字签名如何创建

from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.backends import default_backend
from datetime import datetime

# 生成私钥
private_key = serialization.load_pem_private_key(
    private_key_pem,
    password=None,
    backend=default_backend()
)

# 要签名的数据
data = b"Hello, world!"

# 获取当前时间戳
timestamp = datetime.utcnow().isoformat().encode()

# 将数据和时间戳一起签名
message = data + timestamp
signature = private_key.sign(
    message,
    padding.PSS(
        mgf=padding.MGF1(hashes.SHA256()),
        salt_length=padding.PSS.MAX_LENGTH
    ),
    hashes.SHA256()
)

# 存储签名、数据和时间戳
signed_data = {
    "data": data,
    "timestamp": timestamp,
    "signature": signature
}

# 验证签名
public_key = private_key.public_key()
try:
    public_key.verify(
        signature,
        message,
        padding.PSS(
            mgf=padding.MGF1(hashes.SHA256()),
            salt_length=padding.PSS.MAX_LENGTH
        ),
        hashes.SHA256()
    )
    print("Signature is valid.")
except Exception as e:
    print(f"Signature is invalid: {e}")