The principle and summary of ATITIT.MD5 algorithm

the principle and summary of ATITIT.MD5 algorithm

1 .  MD5 Number of bits 1

2 .  converts a byte array to a four-bit string base16 1

2 . 1. hexadecimal characters are represented by 4 bits. 1

2 . 2. byte[] and hexadecimal strings are converted to each other 2

3 .  base64 notation of MD5 3

4 .  Reference 3

1.MD5 number of digits 128 bits

Generates a byte array that is in bytes:

2.the byte array is converted to a 32-bit string Base16

Every 4 guests can 1111

Just 0--f can fully identify the 4 bit bits.

2.1.hexadecimal characters are represented by 4 bits.

Each character in hexadecimal needs to be represented by a 4-bit bits

2 of four times equals 16. So to use 4 bits to represent a hexadecimal character

Author:: Old Wow's paw attilax Ayron, email:[email protected]

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As shown below:

0	0000
1	0001
2	0010
3	0011
4	0100
5	0101
6	0110
7	0111
8	1000
9	1001
A	1010
B	1011
C	1100
D	1101
E	1110
F	1111

2.2.byte[] and hexadecimal strings are converted to each other

In Java, Byte uses a binary representation of 8 bits, and we know that each character in the 16 binary needs to be represented by a 4-bit bits.

So we can convert each byte to two corresponding 16 characters, that is, the high 4 and low 4 bits of byte are converted to the corresponding 16-character H and L, and combined to get the result of byte conversion to the 16 binary string.

New String (H) + new String (L).

In the same way, the opposite conversion also converts two 16 characters into a byte, as in the same principle.

Based on the above, we can convert the byte[] array to a 16-binary string, and of course we can convert the 16-string to the byte[] array.

3.base64 notation of MD54.Reference

Java byte array and hexadecimal string transfer - Xin Xin Brother's personal page - Open source China Community . htm

Java takes Advantage of messagedigest to get a string or file MD5 detailed - mouse hole - Open source China Community . htm

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The principle and summary of ATITIT.MD5 algorithm