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RSA 非对称加密之分段解密

本贴最后更新于 965 天前，其中的信息可能已经时过境迁

前言：在上一篇文章我们讲到了加密与分段加密，这篇文章我们接着来看解密与分段解密。

一、非对称解密需要用到哪些库

rsa
pip install rsa==4.8
base64
python 自带无需安装

二、非对称解密步骤

加载私钥
预加密计算解密模值
解密/非对称解密

三、分对称解密步骤详解

加载私钥
方式一：

#写死在py文件中
import rsa
import base64

privkey = """
-----BEGIN RSA PRIVATE KEY-----
MIIBOwIBAAJBAJBWZJsSrhwDmtjZkq0hsS0ZSa7JJPvo5gfybdHnRLuZa9jGwfBh
sXFFCJYnZabjQLJ1oPbQ1f7jwbS1WDxI9FkCAwEAAQJABkvuiaFP/SLfH3SmZG0i
2I/Q2hImTeMEHfaiedS37wjwFCjtK12O73ZviLjtpeFyWHcoqEkAhxTvZZfpGNWs
vQIjAMrsJdBGRb3IFktM6+JF6aHAsUPp2Py7tYo++R241U/kAm8CHwC2F1jyw0Lb
o1v/t2dDq6U1/TbpcnfqUI5zzw6HubcCIi2LJM2DCCIZJ0/NOt/1GwOv0NlSQd4v
bwZRLe5Kzq14mkcCHkmlQ7pbssy2U10nRkKeR2GAmhbszwcbsaGxGsVWHQIiE6tW
fSyhJt5DtrAhwkbZwRqWFjovii5QSSzuBmFztnt8VA==
-----END RSA PRIVATE KEY-----
"""
pubkey = """
-----BEGIN RSA PUBLIC KEY-----
MEgCQQCQVmSbEq4cA5rY2ZKtIbEtGUmuyST76OYH8m3R50S7mWvYxsHwYbFxRQiW
J2Wm40CydaD20NX+48G0tVg8SPRZAgMBAAE=
-----END RSA PUBLIC KEY-----
"""
my_pubkey =rsa.PublicKey.load_pkcs1(pubkey)
my_privkey=rsa.PrivateKey.load_pkcs1(privkey)

方式二：

#从pem秘钥文件读取
import rsa
import base64
with open(file="privkey.pem",mode="rb") as file:
    privkey = file.read()
    my_privkey = rsa.PrivateKey.load_pkcs1(keyfile=privkey)
with open(file="pubkey.pem",mode="rb") as file:
    pubkey = file.read()
    my_pubkey = rsa.PublicKey.load_pkcs1(keyfile=pubkey)

预加密计算解密模值

#模长计算公式 = 证书key位数/8 - 11
#证书key位数：一般是512、1024、2048，这个步骤可以问开发，也可以通过加密后密串长度来推算
#证书key位数：动态获取，加密串长度与证书位数对应关系：{'64':512,'128':1024,"512":2048}
# max_encode_len: 加密模长(就是加密分片长度)
# max_decode_len: 解密模长(就是解密分片长度)
#代码演示
def choice_channel():
    msg = "test".encode()
    models_dict={'64':512,'128':1024,"512":2048}
    encrypt_msg = rsa.encrypt(message=msg, pub_key=self.pubkey)
    max_decode_len = len(encrypt_msg)
    key_size = models_dict['{}'.format(max_decode_len)]
    max_encode_len = int(key_size/8-11)
    print("加密模长：",max_encode_len)
    return max_encode_len,max_decode_len

解密/非对称解密

import rsa
import base64

class MyRsa:
    def __init__(self):
        privkey = """
        -----BEGIN RSA PRIVATE KEY-----
        MIIBOwIBAAJBAJBWZJsSrhwDmtjZkq0hsS0ZSa7JJPvo5gfybdHnRLuZa9jGwfBh
        sXFFCJYnZabjQLJ1oPbQ1f7jwbS1WDxI9FkCAwEAAQJABkvuiaFP/SLfH3SmZG0i
        2I/Q2hImTeMEHfaiedS37wjwFCjtK12O73ZviLjtpeFyWHcoqEkAhxTvZZfpGNWs
        vQIjAMrsJdBGRb3IFktM6+JF6aHAsUPp2Py7tYo++R241U/kAm8CHwC2F1jyw0Lb
        o1v/t2dDq6U1/TbpcnfqUI5zzw6HubcCIi2LJM2DCCIZJ0/NOt/1GwOv0NlSQd4v
        bwZRLe5Kzq14mkcCHkmlQ7pbssy2U10nRkKeR2GAmhbszwcbsaGxGsVWHQIiE6tW
        fSyhJt5DtrAhwkbZwRqWFjovii5QSSzuBmFztnt8VA==
        -----END RSA PRIVATE KEY-----
        """
        pubkey = """
        -----BEGIN RSA PUBLIC KEY-----
        MEgCQQCQVmSbEq4cA5rY2ZKtIbEtGUmuyST76OYH8m3R50S7mWvYxsHwYbFxRQiW
        J2Wm40CydaD20NX+48G0tVg8SPRZAgMBAAE=
        -----END RSA PUBLIC KEY-----
        """
        #加载秘钥对象
        self.pubkey =rsa.PublicKey.load_pkcs1(pubkey)
        self.privkey=rsa.PrivateKey.load_pkcs1(privkey)
        #预加密计算模长
        self.max_encode_len,self.max_decode_len = self.choice_channel()

    #预加密，获取模长
    def choice_channel(self):
        msg = "test".encode()
        models_dict={'64':512,'128':1024,"512":2048}
        #加密，获取bytes类型的秘钥长度
        encrypt_msg = rsa.encrypt(message=msg, pub_key=self.pubkey)
        max_decode_len = len(encrypt_msg)
        print("解密模长：", max_decode_len)
        key_size = models_dict['{}'.format(max_decode_len)]
        max_encode_len = int(key_size/8-11)
        print("加密模长：",max_encode_len)
        return max_encode_len,max_decode_len

    #解密
    def decode_string(self,encrypt_msg):
        encrypt_msg = base64.b64decode(encrypt_msg)
        decrypt_str = rsa.decrypt(crypto=encrypt_msg,priv_key=self.privkey)
        new_decrypt_str=decrypt_str.decode()
        print("解密结果：",new_decrypt_str)
        return new_decrypt_str


    #分段解密
    def section_decode(self,msg):
        decode_str = msg.encode()
        decode_str = base64.b64decode(decode_str)
        if len(decode_str) <= self.max_decode_len:
            print("不需要分段解密")
            decode_string = self.decode_string(encrypt_msg=msg)
            print("解密结果：",decode_string)
            return decode_string
        else:
            print("需要分段加密")
            decode_text=[]
            for i in range(0,len(decode_str),self.max_decode_len):
                section_text = decode_str[i:(i + self.max_decode_len)]
                decrypt_str = rsa.decrypt(crypto=section_text, priv_key=self.privkey)
                decode_text.append(decrypt_str)
            decode_byte = b"".join(decode_text)
            decode_string = decode_byte.decode()
            print("解密结果：",decode_string)
            return decode_string

四、完整代码

import rsa
import base64

class MyRsa:
    def __init__(self):
        privkey = """
        -----BEGIN RSA PRIVATE KEY-----
        MIIBOwIBAAJBAJBWZJsSrhwDmtjZkq0hsS0ZSa7JJPvo5gfybdHnRLuZa9jGwfBh
        sXFFCJYnZabjQLJ1oPbQ1f7jwbS1WDxI9FkCAwEAAQJABkvuiaFP/SLfH3SmZG0i
        2I/Q2hImTeMEHfaiedS37wjwFCjtK12O73ZviLjtpeFyWHcoqEkAhxTvZZfpGNWs
        vQIjAMrsJdBGRb3IFktM6+JF6aHAsUPp2Py7tYo++R241U/kAm8CHwC2F1jyw0Lb
        o1v/t2dDq6U1/TbpcnfqUI5zzw6HubcCIi2LJM2DCCIZJ0/NOt/1GwOv0NlSQd4v
        bwZRLe5Kzq14mkcCHkmlQ7pbssy2U10nRkKeR2GAmhbszwcbsaGxGsVWHQIiE6tW
        fSyhJt5DtrAhwkbZwRqWFjovii5QSSzuBmFztnt8VA==
        -----END RSA PRIVATE KEY-----
        """
        pubkey = """
        -----BEGIN RSA PUBLIC KEY-----
        MEgCQQCQVmSbEq4cA5rY2ZKtIbEtGUmuyST76OYH8m3R50S7mWvYxsHwYbFxRQiW
        J2Wm40CydaD20NX+48G0tVg8SPRZAgMBAAE=
        -----END RSA PUBLIC KEY-----
        """
        #加载秘钥对象
        self.pubkey =rsa.PublicKey.load_pkcs1(pubkey)
        self.privkey=rsa.PrivateKey.load_pkcs1(privkey)
        #预加密计算模长
        self.max_encode_len,self.max_decode_len = self.choice_channel()

    #预加密，获取模长
    def choice_channel(self):
        msg = "test".encode()
        models_dict={'64':512,'128':1024,"512":2048}
        encrypt_msg = rsa.encrypt(message=msg, pub_key=self.pubkey)
        max_decode_len = len(encrypt_msg)
        print("解密模长：", max_decode_len)
        key_size = models_dict['{}'.format(max_decode_len)]
        max_encode_len = int(key_size/8-11)
        print("加密模长：",max_encode_len)
        return max_encode_len,max_decode_len

    #加密
    def encode_string(self,string):
        msg = string.encode()
        encrypt_msg = rsa.encrypt(message=msg,pub_key=self.pubkey)
        encrypt_msg = base64.b64encode(encrypt_msg)
        encrypt_msg = encrypt_msg.decode()
        return encrypt_msg

    #解密
    def decode_string(self,encrypt_msg):
        encrypt_msg = base64.b64decode(encrypt_msg)
        decrypt_str = rsa.decrypt(crypto=encrypt_msg,priv_key=self.privkey)
        new_decrypt_str=decrypt_str.decode()
        print("解密结果：",new_decrypt_str)
        return new_decrypt_str

    #分段加密
    def section_encode(self,msg):
        if len(msg) <= self.max_encode_len:
            print("不需要进行分段加密")
            encode_string = self.encode_string(string=msg)
            print("加密结果：", encode_string)
            return encode_string
        else:
            print("需要分段加密")
            encode_text = []
            for i in range(0,len(msg),self.max_encode_len):
                #需要加密的字符串进行切片
                section_text = msg[i:(i+self.max_encode_len)]
                section_text = section_text.encode()
                #分段加密
                encode_str = rsa.encrypt(message=section_text, pub_key=self.pubkey)
                encode_text.append(encode_str)
            #拼接加密后的bytes数据
            encode_bytes = b"".join(encode_text)
            encode_string = base64.b64encode(s=encode_bytes)
            encode_string = encode_string.decode()
            print("分段加密结果：",encode_string)
            return encode_string

    #分段解密
    def section_decode(self,msg):
        decode_str = msg.encode()
        decode_str = base64.b64decode(decode_str)
        if len(decode_str) <= self.max_decode_len:
            print("不需要分段解密")
            decode_string = self.decode_string(encrypt_msg=msg)
            print("解密结果：",decode_string)
            return decode_string
        else:
            print("需要分段加密")
            decode_text=[]
            for i in range(0,len(decode_str),self.max_decode_len):
                section_text = decode_str[i:(i + self.max_decode_len)]
                decrypt_str = rsa.decrypt(crypto=section_text, priv_key=self.privkey)
                decode_text.append(decrypt_str)
            decode_byte = b"".join(decode_text)
            decode_string = decode_byte.decode()
            print("解密结果：",decode_string)
            return decode_string

if __name__ == '__main__':
    cl = MyRsa()
    test_str = "dsdffdsdffasdfasdfdsdffasdfasdfasdfdsdffasdfasdfdsdffasdfasdfdsdffasdfasdfasdf"
    res = cl.section_encode(msg=test_str)
    cl.section_decode(msg=res)
运行结果：
解密模长： 64
加密模长： 53
需要分段加密
分段加密结果： Ud7Pp5w2gz5gFKv0rykptx29+ID7IfrH7Gszkiz3W/QedQM0kv4RDGVWduUEkrO+exh3KC380pTw3/VwHPtTJUzi94321WXMwwwxKAx4eGOLrXfFAaEBjAaHvwNAfavV1+/tV9+QcISBvs+wb0CvQo2Mmh9MBjACP9e/PVZxj1I=
需要分段加密
解密结果： dsdffdsdffasdfasdfdsdffasdfasdfasdfdsdffasdfasdfdsdffasdfasdfdsdffasdfasdfasdf

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