同态加密计算银行交易总和时解密失败问题求助

你遇到的解密失败问题，核心原因是Paillier同态加密算法（LightPHE实现的版本）原生仅支持整数运算，而你直接加密了浮点数类型的交易金额，导致加密和解密过程中数据被异常处理，无法正确还原总和。

将浮点数金额转换为整数（比如把美元金额乘以100，转为以“分”为单位的整数），完成加密、同态加法、解密后，再转换回浮点数即可。以下是修改后的完整代码：

import tkinter as tk
import csv
import random
import time
from lightphe import LightPHE

def generate_and_write_transactions(filename, num_transactions):
    transactions = []
    for _ in range(num_transactions):
        amount_received = round(random.uniform(10, 500), 2)  
        transactions.append(("Deposit", amount_received))
    
    with open(filename, "w", newline="") as csvfile:
        csvwriter = csv.writer(csvfile)
        csvwriter.writerow(["Transaction Type", "Amount"])
        csvwriter.writerows(transactions)

def compute_total_amount():
    try:
        start_time = time.time()
        filename = "transaction_history.csv"
        total_amount = 0
        
        with open(filename, 'r') as file:
            reader = csv.reader(file)
            next(reader)  # 跳过表头
            for row in reader:
                if row[0] == 'Deposit':
                    total_amount += float(row[1])
        
        end_time = time.time()
        result_label.config(text=f"传统计算总金额: ${total_amount:.2f}\n耗时: {end_time - start_time:.6f} 秒")
    except Exception as e:
        result_label.config(text="错误: " + str(e))

def compute_total_amount_homomorphic():
    try:
        start_time = time.time()
        filename = "transaction_history.csv"

        cs = LightPHE(algorithm_name="Paillier")
        
        encrypted_values = []  

        with open(filename, 'r') as file:
            reader = csv.reader(file)
            next(reader)  
            for row in reader:
                if row[0] == 'Deposit':
                    # 将浮点数金额转为整数（乘以100，转为分）
                    amount_int = int(round(float(row[1]) * 100))
                    encrypted_amount = cs.encrypt(plaintext=amount_int)
                    encrypted_values.append(encrypted_amount)
        
        # 同态累加所有加密值
        total_encrypted_sum = encrypted_values[0]
        for encrypted_amount in encrypted_values[1:]:
            total_encrypted_sum += encrypted_amount
        
        # 解密总和并转换回浮点数
        total_sum_decrypted = cs.decrypt(total_encrypted_sum)
        total_amount = total_sum_decrypted / 100.0
        
        end_time = time.time()
        
        result_text = f"同态加密计算总金额: ${total_amount:.2f}\n耗时: {end_time - start_time:.6f} 秒"
        result_label.config(text=result_text)
    except Exception as e:
        result_label.config(text="错误: " + str(e))

generate_and_write_transactions("transaction_history.csv", 10)

root = tk.Tk()
root.title("银行账户测试")

root.geometry("400x300") 

compute_button = tk.Button(root, text="传统方式计算总金额", command=compute_total_amount)
compute_button.pack(pady=5)

compute_homomorphic_button = tk.Button(root, text="同态加密方式计算总金额", command=compute_total_amount_homomorphic)
compute_homomorphic_button.pack(pady=5)

result_label = tk.Label(root, text="")
result_label.pack()

root.mainloop()

• 加密前转换：将交易金额float(row[1])乘以100并转为整数，确保输入Paillier加密的是整数类型
• 解密后还原：解密得到整数总和后，除以100.0恢复为原金额格式，并用round处理精度问题
• 这样修改后，同态加密的计算结果会和传统计算结果一致，且能正常解密显示

内容的提问来源于stack exchange，提问作者Marian