About PHP MD5 16-bit raw binary output with 32-bit string output

About PHP MD5 16-bit raw binary output and 32-bit string output

Because PHP AES is required to encrypt data, consider using PHP MD5 to output 16-bit binary as the key.

Google a bit "php MD5 16"? I found a lot of articles that are suggested to be implemented by intercepting strings, and the statements are as follows:

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Perhaps they need a random string of 16 bits in length, and more likely they understand the true meaning of MD5.

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ERLANG:MD5 ("AAA"). Percent output:<<71,188,229,199,79,88,159,72,103,219,213,126,156,169,248,8>>

From the above statement can be seen, ERLANG:MD5 output a 16-bit binary data, each bit for the 8bit,16*8 total 128bits.

That is, the MD5 output is a set of 16-bit (16Byte) 128bits of data.

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PHP:MD5 ("AAA")//output: 47bce5c74f589f4867dbd57e9ca9f808

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The MD5 binary format and HEX String?format tables are as follows:

Binary	71	188	229	199	79	88	159	72	103	219	213	126	156	169	248	8
16 Binary notation:	47	Bc	E5	C7	4f	58	9f	48	67	Db	D5	7e	9c	A9	F8	08

71 If the hexadecimal representation is 47; 1886 binary is BC, and so on.

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Now let's look at Php's MD5 function:

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PHP:MD5 ("AAA") output 32-bit length string: 08, BC, E5, C7, 4f,, 9f, A9,, DB, D5, 7e, 9c, F8

In fact, the equivalent of 16byte binary data with hex. Similar to color rgb (255,255,255) = #FF ff ff.

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PHP:MD5 ("AAA", ture) outputs 16byte binary data. Binary data parsing is as follows:?

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$bin = MD5 ("AAA", ture); for ($a =0; $a
 
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