day07 7.2 常用加密

【1】字符串与字节

反编译回来的代码有些字符串使用字节表示
- 隐藏真正字符串

String salt = "sign";
System.out.println(Arrays.toString(salt.getBytes()));
String v4 = new String(new byte[]{115, 105, 103, 110});
System.out.println(salt);
System.out.println(v4);

python转换

v1 = [115, 105, 103, 110]
def java_arr_to_python_str(v1):
    num_list = bytearray()
    for i in v1:
        if i < 0:
            i = i + 256
        num_list.append(i)
    return num_list.decode('utf-8')


if __name__ == '__main__':
    print(java_arr_to_python_str(v1))

【2】UUID

import java.util.UUID;

public class Hello {
    public static void main(String[] args){
        String uid = UUID.randomUUID().toString();
        System.out.println(uid);
    }
}

// python
import uuid
uid = str(uuid.uuid4())
print(uid)

![3](imgs/day07 7.1 Java中的面向对象之类与对象.assets/3.png)

【3】随机值

java

// 随机生成80位，10个字节
BigInteger v4 = new BigInteger(80, new SecureRandom());
// 让字节以16进制展示
String res = v4.toString(16);
System.out.println(res);

python3.9+

# python 3.9
import random
data = random.randbytes(10)  # python3.9
ele_list = []
for item in data:
    ele = hex(item)[2:]
    ele_list.append(ele)
res = "".join(ele_list)
print(res)
# 或者
import random
data = "".join([hex(item)[2:] for item in random.randbytes(10)])
print(data)

python3.9-

# 3.9以前
import random
byte_list = [random.randint(0, 255) for i in range(10)]
print([item for item in byte_list])
print([hex(item)[2:] for item in byte_list])
print([hex(item)[2:].rjust(2, "0") for item in byte_list])

print("".join([hex(item)[2:].rjust(2, "0") for item in byte_list]))

【4】时间戳

String t1 = String.valueOf(System.currentTimeMillis() / 1000); // 秒级别
String t2 = String.valueOf(System.currentTimeMillis()); // 毫秒级别

System.out.println(t1);
System.out.println(t2);

![4](imgs/day07 7.1 Java中的面向对象之类与对象.assets/4.png)

python

import time

v1 = int(time.time()) # 秒级别
v2 = int(time.time()*1000)# 毫秒级别
print(v1)
print(v2)

【5】十六进制的字符串

![5](imgs/day07 7.1 Java中的面向对象之类与对象.assets/5.png)

s='pengyuyan'.encode('utf-8')
l=[]
for i in s:
    l.append(hex(i)[2:].rjust(2,'0')) # 转16进制，只去后两位，如果不足两位，补0
print(l)

【6】md5

![6](imgs/day07 7.1 Java中的面向对象之类与对象.assets/6.png)

import hashlib
obj = hashlib.md5('yyy'.encode('utf-8'))
obj.update('xxxxx'.encode('utf-8'))

# java中没有这个功能,把每个字节转换成16进制
v1 = obj.hexdigest()
print(v1) # d3c0aaaf596e3299f695591f00fd75cb

v2 = obj.digest()
print(v2) # b'\xd3\xc0\xaa\xafYn2\x99\xf6\x95Y\x1f\x00\xfdu\xcb'

【7】base64编码

java

String name = "彭于晏";
// 编码
Base64.Encoder encoder  = Base64.getEncoder();
String res = encoder.encodeToString(name.getBytes());
System.out.println(res); //5b2t5LqO5pmP

// 解码
Base64.Decoder decoder  = Base64.getDecoder();
byte[] origin = decoder.decode(res);
String data = new String(origin);
System.out.println(data); // 彭于晏

python

import base64

name = "彭于晏"
res = base64.b64encode(name.encode('utf-8'))
print(res) # b'5b2t5LqO5pmP'

data = base64.b64decode(res)
origin = data.decode('utf-8')
print(origin) # "彭于晏"