如何使用Base64进行加密和解密

Knight94

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原创最新推荐文章于 2026-04-15 17:25:55 发布 9.6k 阅读 AI 写同款· GEO 优化 ›

Base64的加密与解密最近对网络安全的兴趣猛涨，闲着没逝，给大家整一期Base64的加密与解密。阅读详情

其实Base64的加密和解密的算法不是很复杂，首先是定义自己64位的密钥，64个字符是固定，但是顺序是可以随自己的设计而变化。例如：

char[] BaseTable=new char[64]{

'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',

'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',

'0','1','2','3','4','5','6','7','8','9','+','/'};

接下来，在加密的时候就是对于需要加密的每个字符，通过一定的算法，转换成上面64字符的一种；而在解密的时候则是把64字符中任意一个字符反算出加密前的字符。对于每个字符的操作有很多方法，这里就不一一介绍了。需要注意的是“=”字符，在Base64加密算法中，是很重要的，它是起到补零作用。

以下是完整代码：

//----------------------------- Base64 class --------------------------------------

//---------------------------------------------------------------------------------

//---File:clsBase64

//---Description:The class file to encode string or decode string in base algorith

//---Author:Knight

//---Date:Oct.8, 2005

//---------------------------------------------------------------------------------

//----------------------------{ Base64 class }-------------------------------------

using System;

namespace Base64

{

/// <summary>

/// Summary description for clsBase64.

/// </summary>

public class clsBase64

{

private char[] source;

private char[] lookupTable;

private int length, length2, length3;

private int blockCount;

private int paddingCount;

public clsBase64()

{

// TODO: Add constructor logic here

source = null;

length = length2 = length3 =0;

blockCount = 0;

paddingCount = 0;

}

/// <summary>

/// Create base64 char array using default base64 char array

/// </summary>

/// <param name="CreatePara"></param>

/// <returns>return the new base64 char array</returns>

private char[] CreateBase64Char( ref char[] CreatePara )

{

char[] BaseTable=new char[64]{

'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',

'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',

'0','1','2','3','4','5','6','7','8','9','+','/'};

const int CREATE_TYPE = 8;

byte bParaValue = 0;

byte bTemp;

for( int i = 0; i < CreatePara.Length; i++ )

{

bTemp = ( byte )( CreatePara[i] );

switch( bTemp % CREATE_TYPE )

{

case 1:

// 00000001

bTemp =( byte )( bTemp ^ 0x01 );

break;

case 2:

// 00000010

bTemp =( byte )( bTemp ^ 0x02 );

break;

case 3:

// 00000100

bTemp =( byte )( bTemp ^ 0x04 );

break;

case 4:

// 00001000

bTemp =( byte )( bTemp ^ 0x08 );

break;

case 5:

// 00010000

bTemp =( byte )( bTemp ^ 0x10 );

break;

case 6:

// 00100000

bTemp =( byte )( bTemp ^ 0x20 );

break;

case 7:

// 01000000

bTemp =( byte )( bTemp ^ 0x40 );

break;

default:

// 10000000

bTemp =( byte )( bTemp ^ 0x80 );

break;

}

bParaValue =( byte )( bParaValue ^ bTemp );

}

char chrTemp;

int nIndex;

switch( bParaValue % CREATE_TYPE )

{

case 1:

// Exechange 0 <--> 1, 2 <--> 3, 4 <--> 5, 6 <--> 7

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = chrTemp;

chrTemp = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = chrTemp;

chrTemp = BaseTable[nIndex + 4];

BaseTable[nIndex + 4] = BaseTable[nIndex + 5];

BaseTable[nIndex + 5] = chrTemp;

chrTemp = BaseTable[nIndex + 6];

BaseTable[nIndex + 6] = BaseTable[nIndex + 7];

BaseTable[nIndex + 7] = chrTemp;

}

break;

case 2:

// Exechange 0 <--> 2, 1 <--> 3, 4 <--> 6, 5 <--> 7

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = chrTemp;

chrTemp = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = chrTemp;

chrTemp = BaseTable[nIndex + 4];

BaseTable[nIndex + 4] = BaseTable[nIndex + 6];

BaseTable[nIndex + 6] = chrTemp;

chrTemp = BaseTable[nIndex + 5];

BaseTable[nIndex + 5] = BaseTable[nIndex + 7];

BaseTable[nIndex + 7] = chrTemp;

}

break;

case 3:

// Exechange 0 <--> 3, 1 <--> 2, 4 <--> 7, 5 <--> 6

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = chrTemp;

chrTemp = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = chrTemp;

chrTemp = BaseTable[nIndex + 4];

BaseTable[nIndex + 4] = BaseTable[nIndex + 7];

BaseTable[nIndex + 7] = chrTemp;

chrTemp = BaseTable[nIndex + 5];

BaseTable[nIndex + 5] = BaseTable[nIndex + 6];

BaseTable[nIndex + 6] = chrTemp;

}

break;

case 4:

// Mirror exechange

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + CREATE_TYPE - 1];

BaseTable[nIndex + CREATE_TYPE - 1] = chrTemp;

chrTemp = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = BaseTable[nIndex + CREATE_TYPE - 2];

BaseTable[nIndex + CREATE_TYPE - 2] = chrTemp;

chrTemp = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = BaseTable[nIndex + CREATE_TYPE - 3];

BaseTable[nIndex + CREATE_TYPE - 3] = chrTemp;

chrTemp = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = BaseTable[nIndex + CREATE_TYPE - 4];

BaseTable[nIndex + CREATE_TYPE - 4] = chrTemp;

}

break;

case 5:

// Exechange 0 <--> 4, 1 <--> 5, 2 <--> 6, 3 <--> 7

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + 4];

BaseTable[nIndex + 4] = chrTemp;

chrTemp = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = BaseTable[nIndex + 5];

BaseTable[nIndex + 5] = chrTemp;

chrTemp = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = BaseTable[nIndex + 6];

BaseTable[nIndex + 6] = chrTemp;

chrTemp = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = BaseTable[nIndex + 7];

BaseTable[nIndex + 7] = chrTemp;

}

break;

case 6:

// Exechange 0 <--> 5, 1 <--> 6, 2 <--> 7, 3 <--> 4

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + 5];

BaseTable[nIndex + 5] = chrTemp;

chrTemp = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = BaseTable[nIndex + 6];

BaseTable[nIndex + 6] = chrTemp;

chrTemp = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = BaseTable[nIndex + 7];

BaseTable[nIndex + 7] = chrTemp;

chrTemp = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = BaseTable[nIndex + 4];

BaseTable[nIndex + 4] = chrTemp;

}

break;

case 7:

// Exechange 0 <--> 6, 1 <--> 7, 2 <--> 4, 3 <--> 5

for( int i = 0; i < BaseTable.Length / CREATE_TYPE; i++ )

{

nIndex = i * CREATE_TYPE;

chrTemp = BaseTable[nIndex];

BaseTable[nIndex] = BaseTable[nIndex + 6];

BaseTable[nIndex + 6] = chrTemp;

chrTemp = BaseTable[nIndex + 1];

BaseTable[nIndex + 1] = BaseTable[nIndex + 7];

BaseTable[nIndex + 7] = chrTemp;

chrTemp = BaseTable[nIndex + 2];

BaseTable[nIndex + 2] = BaseTable[nIndex + 4];

BaseTable[nIndex + 4] = chrTemp;

chrTemp = BaseTable[nIndex + 3];

BaseTable[nIndex + 3] = BaseTable[nIndex + 5];

BaseTable[nIndex + 5] = chrTemp;

}

break;

default:

break;

}

return BaseTable;

}

/// <summary>

/// Encode string at specific parameter

/// </summary>

/// <param name="Para"></param>

/// <param name="input"></param>

/// <returns>return encoded string</returns>

public char[] GetEncoded( char[] Para, byte[] input )

{

length=input.Length;

if((length % 3)==0)

{

paddingCount=0;

blockCount=length/3;

}

else

{

paddingCount=3-(length % 3);//need to add padding

blockCount=(length+paddingCount) / 3;

}

length2=length+paddingCount;//or blockCount *3

byte[] source2;

source2=new byte[length2];

//copy data over insert padding

for (int x=0; x<length2;x++)

{

if (x<length)

{

source2[x]=input[x];

}

else

{

source2[x]=0;

}

byte b1, b2, b3;

byte temp, temp1, temp2, temp3, temp4;

byte[] buffer=new byte[blockCount*4];

char[] result=new char[blockCount*4];

for (int x=0;x<blockCount;x++)

{

b1=source2[x*3];

b2=source2[x*3+1];

b3=source2[x*3+2];

temp1=(byte)((b1 & 252)>>2);//first

temp=(byte)((b1 & 3)<<4);

temp2=(byte)((b2 & 240)>>4);

temp2+=temp; //second

temp=(byte)((b2 & 15)<<2);

temp3=(byte)((b3 & 192)>>6);

temp3+=temp; //third

temp4=(byte)(b3 & 63); //fourth

buffer[x*4]=temp1;

buffer[x*4+1]=temp2;

buffer[x*4+2]=temp3;

buffer[x*4+3]=temp4;

}

lookupTable = CreateBase64Char( ref Para );

for (int x=0; x<blockCount*4;x++)

{

result[x]=sixbit2char(buffer[x]);

}

//covert last "A"s to "=", based on paddingCount

switch (paddingCount)

{

case 0:break;

case 1:result[blockCount*4-1]='=';break;

case 2:result[blockCount*4-1]='=';

result[blockCount*4-2]='=';

break;

default:break;

}

return result;

}

private char sixbit2char(byte b)

{

if((b>=0) &&(b<=63))

{

return lookupTable[(int)b];

}

else

{

//should not happen;

return ' ';

}

/// <summary>

/// Decode string using specific parameter

/// </summary>

/// <param name="Para"></param>

/// <param name="input"></param>

/// <returns>If decoded successfully, return the decoded string; else return NULL</returns>

public byte[] GetDecoded( char[] Para, char[] input )

{

int temp=0;

source=input;

length=input.Length;

if( ( length % 4 ) != 0 ) return null; // The string is not encoded with my base64;

//find how many padding there are

while( input[length - temp - 1] == '=' && temp < 3 )

{

temp++;

}

if( temp == 3 ) return null; // The string is not encoded with my base64;

paddingCount=temp;

//calculate the blockCount;

//assuming all whitespace and carriage returns/newline were removed.

blockCount=length/4;

length2=blockCount*3;

byte[] buffer=new byte[length];//first conversion result

byte[] buffer2=new byte[length2];//decoded array with padding

lookupTable = CreateBase64Char( ref Para );

for(int x=0;x<length;x++)

{

buffer[x]=char2sixbit(source[x]);

}

byte b, b1,b2,b3;

byte temp1, temp2, temp3, temp4;

for(int x=0;x<blockCount;x++)

{

temp1=buffer[x*4];

temp2=buffer[x*4+1];

temp3=buffer[x*4+2];

temp4=buffer[x*4+3];

b=(byte)(temp1<<2);

b1=(byte)((temp2 & 48)>>4);

b1+=b;

b=(byte)((temp2 & 15)<<4);

b2=(byte)((temp3 & 60)>>2);

b2+=b;

b=(byte)((temp3 & 3)<<6);

b3=temp4;

b3+=b;

buffer2[x*3]=b1;

buffer2[x*3+1]=b2;

buffer2[x*3+2]=b3;

}

//remove paddings

length3=length2-paddingCount;

byte[] result=new byte[length3];

for(int x=0;x<length3;x++)

{

result[x]=buffer2[x];

}

return result;

}

private byte char2sixbit(char c)

{

if( c=='=' )

return 0;

else

{

for (int x=0;x<64;x++)

{

if (lookupTable[x]==c)

return (byte)x;

}

//should not reach here

return 0;

}

收录于

高级编程（c#）

标签

#加密 #byte #buffer #string #whitespace

密码学：一文看懂Base64算法 Base64常常在我们开发中出现，我们可能只知道它是一串乱码（看不懂的符号），知道有时候知道我们需要把一些数据进行base64编码，有时候需要进行Base64解码。但是却不知道它的作用是什么？它存在的意义是什么？还有它是如何生成的？如何编码和解码？上述的疑问相信在你读完本篇文章之后烟消云散。下面开始正文。Base64是什么?它和加密解密操作有什么关系吗?没错，这就是经过Base64编码后的字符串。对它解码后，我们获得以下内容点个关注，是对我持续创作的最大的鼓励！阅读详情

如何使用Base64进行加密和解密

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