From 73e9c6786ff68ee78a2bbaab4669c2d006e8ac3e Mon Sep 17 00:00:00 2001
From: Sky Johnson <skylearj@gmail.com>
Date: Thu, 31 Jul 2025 21:40:47 -0500
Subject: [PATCH] first commit

---
 md5.cpp | 138 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 md5.cpp

diff --git a/md5.cpp b/md5.cpp
new file mode 100644
index 0000000..5351476
--- /dev/null
+++ b/md5.cpp
@@ -0,0 +1,138 @@
+#include <iostream>
+#include <iomanip>
+#include <string>
+#include <vector>
+#include <cstring>
+#include <cstdint>
+#include <bit>
+#include <format>
+
+class MD5 {
+private:
+	static constexpr uint32_t S[64] = {
+		7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
+		5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20,
+		4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
+		6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
+	};
+	
+	static constexpr uint32_t K[64] = {
+		0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
+		0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
+		0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
+		0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
+		0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
+		0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
+		0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
+		0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
+		0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
+		0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
+		0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
+		0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
+		0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
+		0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
+		0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
+		0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
+	};
+
+	uint32_t h[4] = {0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476};
+
+	static uint32_t F(uint32_t x, uint32_t y, uint32_t z) {
+		return (x & y) | (~x & z);
+	}
+
+	static uint32_t G(uint32_t x, uint32_t y, uint32_t z) {
+		return (x & z) | (y & ~z);
+	}
+
+	static uint32_t H(uint32_t x, uint32_t y, uint32_t z) {
+		return x ^ y ^ z;
+	}
+
+	static uint32_t I(uint32_t x, uint32_t y, uint32_t z) {
+		return y ^ (x | ~z);
+	}
+
+	void processBlock(const uint8_t* block) {
+		uint32_t w[16];
+		std::memcpy(w, block, 64);
+
+		uint32_t a = h[0], b = h[1], c = h[2], d = h[3];
+
+		for (int i = 0; i < 64; ++i) {
+			uint32_t f, g;
+			
+			if (i < 16) {
+				f = F(b, c, d);
+				g = i;
+			} else if (i < 32) {
+				f = G(b, c, d);
+				g = (5 * i + 1) % 16;
+			} else if (i < 48) {
+				f = H(b, c, d);
+				g = (3 * i + 5) % 16;
+			} else {
+				f = I(b, c, d);
+				g = (7 * i) % 16;
+			}
+
+			f += a + K[i] + w[g];
+			a = d;
+			d = c;
+			c = b;
+			b += std::rotl(f, S[i]);
+		}
+
+		h[0] += a;
+		h[1] += b;
+		h[2] += c;
+		h[3] += d;
+	}
+
+public:
+	std::string hash(const std::string& input) {
+		h[0] = 0x67452301;
+		h[1] = 0xefcdab89;
+		h[2] = 0x98badcfe;
+		h[3] = 0x10325476;
+
+		std::vector<uint8_t> data(input.begin(), input.end());
+		uint64_t originalLength = data.size() * 8;
+
+		data.push_back(0x80);
+
+		while (data.size() % 64 != 56) {
+			data.push_back(0);
+		}
+
+		for (int i = 0; i < 8; ++i) {
+			data.push_back((originalLength >> (i * 8)) & 0xff);
+		}
+
+		for (size_t i = 0; i < data.size(); i += 64) {
+			processBlock(&data[i]);
+		}
+
+		std::string result;
+		for (int i = 0; i < 4; ++i) {
+			for (int j = 0; j < 4; ++j) {
+				uint8_t byte = (h[i] >> (j * 8)) & 0xff;
+				result += std::format("{:02x}", byte);
+			}
+		}
+
+		return result;
+	}
+};
+
+int main() {
+	MD5 md5;
+	
+	std::cout << md5.hash("") << std::endl;
+	std::cout << md5.hash("a") << std::endl;
+	std::cout << md5.hash("abc") << std::endl;
+	std::cout << md5.hash("message digest") << std::endl;
+	std::cout << md5.hash("abcdefghijklmnopqrstuvwxyz") << std::endl;
+	
+	return 0;
+}
\ No newline at end of file