notes.txt

requirements :
Makefile, author file
C, Norm

allowed functions :

open, close, read, write, malloc, free

tolerated if necessary :
strerror, exit

---------- openssl

executable : ft_ssl

Standard commands :
	next project ?

Message Digest commands :

options : {
	-p : echo STDIN to STDOUT and append the checksum to STDOUT
		 -q and -p do not modifiy output
		 only applies to STDIN
		> echo "Do not pity the dead, Harry." | ./ft_ssl md5 -p
		Do not pity the dead, Harry.
		2d95365bc44bf0a298e09a3ab7b34d2f

	-q : quiet mode
		does not print name ?

	-r : reverse the format of the input
		> ./ft_ssl md5 file
		MD5 (file) = 53d53ea94217b259c11a5a2d104ec58a
		> ./ft_ssl md5 -r file
		53d53ea94217b259c11a5a2d104ec58a file

	-s : print the sum of the given string (first arg is not a file) (applies only once)
		> ./ft_ssl md5 -s "pity those that aren't following baerista on spotify."
		MD5 ("pity those that aren't following baerista on spotify.") = a3c990a1964705d9bf0e602f44572f5f
		> echo "one more thing" | ./ft_ssl md5 -r -p -s "foo" file -s "bar"
		one more thing
		a0bd1876c6f011dd50fae52827f445f5
		acbd18db4cc2f85cedef654fccc4a4d8 "foo"
		53d53ea94217b259c11a5a2d104ec58a file
		ft_ssl: md5: -s: No such file or directory
		ft_ssl: md5: bar: No such file or directory

	no opt	: read/write from/to the console
}

syntax : {
	./ft_ssl command [files]
}

must support : {
	STDIN
	STDOUT
	files
}

md5 {
	md5
	openssl md5
	./ft_ssl md5

	len : 32 hexadecimal (128 bits) (4 * 32-bit words : A, B, C, D) (4 * 4 bytes)
	Merkle–Damgård construction (https://en.wikipedia.org/wiki/Merkle%E2%80%93Damg%C3%A5rd_construction)

	MD5("") = d41d8cd98f00b204e9800998ecf8427e

	message padding (bits) :
		first bit : 1
		as many 0 necessary to obtain a length up to 64 bits (8 bytes) fewer than a multiple of 512 (64 bytes)
		64 bits (8 bytes) representing the length of the message, modulo 2^64
	split into 512-bit blocks (16*32-bit words)

	main algorithm :
		A, B, C, D initialized to predetermined fixed constants
		for each 512-bit block : modify the state in four rounds
		each round is composed of 16 similar operations based on a non-linear function F, modular addition, and left rotation
		avalanche effect
		{
			possible functions :
			values in little-endian

			F(B, C, D) = (B & C) | (~B & D)
			G(B, C, D) = (B & D) | (C & ~D)
			H(B, C, D) = B ^ C ^ D
			I(B, C, D) = C ^ (B | ~D)
		}
		{
			& 	bitwise AND
			| 	bitwise inclusive OR
			^ 	bitwise XOR (exclusive OR)
			<< 	left shift
			>> 	right shift
			~ 	bitwise NOT (one's complement) (unary)
		}

	a = 0x67452301
	b = 0xefcdab89
	c = 0x98badcfe
	d = 0x10325476

	abcd -> dabc -> cdab -> bcda

	f : 7 12 17 22
	0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee
	0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501
	0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be
	0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821
	g : 5 9 14 20
	0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa
	0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8
	0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed
	0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a
	h : 4 11 7 23
	0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c
	0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70
	0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05
	0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665
	i : 6 10 15 21
	0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039
	0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1
	0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1
	0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391

}

sha256 {
	sha256 (man unavailable on macs)
	openssl sha -256
	./ft_ssl sha256

	test with shasum

	len : 64 c

	Big-endian convention is used when expressing the constants in this pseudocode, and when parsing message block data from bytes to words, for example, the first word of the input message "abc" after padding is 0x61626380


	h0 = 0x6a09e667
	h1 = 0xbb67ae85
	h2 = 0x3c6ef372
	h3 = 0xa54ff53a
	h4 = 0x510e527f
	h5 = 0x9b05688c
	h6 = 0x1f83d9ab
	h7 = 0x5be0cd19

	k = {
	   0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
	   0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
	   0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
	   0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
	   0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
	   0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
	   0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
	   0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
	}
}

bonus {
	sha512
	whirlpool
}

Cipher commands :
	next project ?