diff --git a/include/md5_internal.h b/include/md5_internal.h
new file mode 100644
index 0000000..95b2402
--- /dev/null
+++ b/include/md5_internal.h
@@ -0,0 +1,8 @@
+#ifndef MD5_INTERNAL_H
+#define MD5_INTERNAL_H
+
+#include "md5.h"
+
+void	md5_compress(struct md5_ctx *ctx, const uint8_t block[64]);
+
+#endif
diff --git a/src/Makefile.am b/src/Makefile.am
index c2a7e07..ca5ff1c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -3,6 +3,7 @@ lib_LTLIBRARIES				= libft_ssl.la
 libft_ssl_la_SOURCES		= libft_ssl.c \
 							  md5/md5.c \
 							  md5/md5_init.c \
+							  md5/md5_compress.c \
 							  md5/md5_update.c \
 							  md5/md5_final.c \
 							  sha256/sha256_init.c \
diff --git a/src/md5/md5_compress.c b/src/md5/md5_compress.c
new file mode 100644
index 0000000..921ee9b
--- /dev/null
+++ b/src/md5/md5_compress.c
@@ -0,0 +1,124 @@
+#include "md5_internal.h"
+#include <stdint.h>
+
+/* Forward declrations */
+typedef uint32_t (*md5_round_fn)(uint32_t, uint32_t, uint32_t);
+typedef uint32_t (*md5_k_fn)(uint8_t);
+
+static uint32_t	md5_f(uint32_t b, uint32_t c, uint32_t d);
+static uint32_t	md5_g(uint32_t b, uint32_t c, uint32_t d);
+static uint32_t	md5_h(uint32_t b, uint32_t c, uint32_t d);
+static uint32_t	md5_i(uint32_t b, uint32_t c, uint32_t d);
+static uint32_t	md5_k0(uint8_t i);
+static uint32_t	md5_k1(uint8_t i);
+static uint32_t	md5_k2(uint8_t i);
+static uint32_t	md5_k3(uint8_t i);
+static uint32_t	md5_leftrotate(uint32_t x, uint32_t n);
+static void		md5_decode(const uint8_t block[64], uint32_t m[16]);
+/* ------------------- */
+
+static const md5_round_fn	round_fns[4] = { md5_f, md5_g, md5_h, md5_i };
+static const md5_k_fn		round_k[4] = { md5_k0, md5_k1, md5_k2, md5_k3 };
+
+void
+md5_compress(struct md5_ctx *ctx, const uint8_t block[64])
+{
+	uint32_t	m[16];
+	uint32_t	a, b, c, d;
+	uint32_t	temp;
+
+	md5_decode(block, m);
+
+	a = ctx->state[0];
+	b = ctx->state[1];
+	c = ctx->state[2];
+	d = ctx->state[3];
+
+	for (uint8_t i = 0; i < 64; ++i)
+	{
+		const uint8_t idx = (i / 16) & 3;
+		const uint32_t k = round_k[idx](i);
+
+		temp = a + round_fns[idx](b, c, d) + m[k] + g_md5_T[i];
+		temp = md5_leftrotate(temp, g_md5_s[i]) + b;
+		a = d; d = c; c = b; b = temp;
+	}
+
+	ctx->state[0] += a;
+	ctx->state[1] += b;
+	ctx->state[2] += c;
+	ctx->state[3] += d;
+}
+
+
+/* Decode 64 bytes into 16 x uint32_t words (little-endian) */
+static void
+md5_decode(const uint8_t block[64], uint32_t m[16])
+{
+	for (uint8_t i = 0; i < 16; ++i)
+	{
+		const uint8_t	i4 = i * 4;
+
+		m[i] = (uint32_t)block[i4 + 0] << 0
+			 | (uint32_t)block[i4 + 1] << 8
+			 | (uint32_t)block[i4 + 2] << 16
+			 | (uint32_t)block[i4 + 3] << 24;
+	}
+}
+
+/* Round functions */
+static uint32_t
+md5_f(uint32_t b, uint32_t c, uint32_t d)
+{
+	return (b & c) | (~b & d);
+}
+
+static uint32_t
+md5_g(uint32_t b, uint32_t c, uint32_t d)
+{
+	return (b & d) | (c & ~d);
+}
+
+static uint32_t
+md5_h(uint32_t b, uint32_t c, uint32_t d)
+{
+	return b ^ c ^ d;
+}
+
+static uint32_t
+md5_i(uint32_t b, uint32_t c, uint32_t d)
+{
+	return c ^ (b | ~d);
+}
+
+/* k selectors */
+static uint32_t
+md5_k0(uint8_t i)
+{
+	return (uint32_t)i;
+}
+
+static uint32_t
+md5_k1(uint8_t i)
+{
+	return (uint32_t)((1 + 5 * i) & 15);
+}
+
+static uint32_t
+md5_k2(uint8_t i)
+{
+	return (uint32_t)((5 + 3 * i) & 15);
+}
+
+static uint32_t
+md5_k3(uint8_t i)
+{
+	return (uint32_t)((7 * i) & 15);
+}
+
+
+static uint32_t
+md5_leftrotate(uint32_t x, uint32_t n)
+{
+	return (x << n) | (x >> (32u - n));
+}
diff --git a/src/md5/md5_final.c b/src/md5/md5_final.c
index fc2f898..21c359f 100644
--- a/src/md5/md5_final.c
+++ b/src/md5/md5_final.c
@@ -1,6 +1,56 @@
-#include "compiler.h"
-#include "md5.h"
+#include "md5_internal.h"
+#include <stdint.h>
 
-void	md5_final(__unused void *ctx, __unused uint8_t *out)
+/* Forward declarations */
+static void			md5_pad(struct md5_ctx *ctx);
+static inline void	md5_write_len(struct md5_ctx *ctx, uint64_t bitlen);
+static void			md5_encode(const struct md5_ctx *ctx, uint8_t out[16]);
+/* ---------------- */
+
+void	md5_final(void *ctx, uint8_t *out)
 {
+	struct md5_ctx	*local_ctx = ctx;
+
+	md5_pad(local_ctx);
+	md5_encode(local_ctx, out);
+}
+
+static void
+md5_pad(struct md5_ctx *ctx)
+{
+	uint64_t	bitlen = ctx->count * 8;
+
+	ctx->buf[ctx->count++ & 63] = 0x80;
+	if ((ctx->count & 63) > 56)
+	{
+		while ((ctx->count & 63) != 0)
+			ctx->buf[ctx->count++ & 63] = 0x00;
+		md5_compress(ctx, ctx->buf);
+	}
+	while ((ctx->count & 63) < 56)
+		ctx->buf[ctx->count++ & 63] = 0x00;
+	md5_write_len(ctx, bitlen);
+	md5_compress(ctx, ctx->buf);
+}
+
+static inline void
+md5_write_len(struct md5_ctx *ctx, uint64_t bitlen)
+{
+	for (uint8_t i = 0; i < 8; ++i)
+		ctx->buf[56 + i] = (uint8_t)(bitlen >> (8 * i));
+}
+
+static void
+md5_encode(const struct md5_ctx *ctx, uint8_t out[16])
+{
+	for (uint8_t i = 0; i < 4; ++i)
+		{
+			const uint8_t	i4 = i * 4;
+			uint32_t 		v = ctx->state[i];
+
+			out[i4 + 0] = (uint8_t)(v >> 0);
+			out[i4 + 1] = (uint8_t)(v >> 8);
+			out[i4 + 2] = (uint8_t)(v >> 16);
+			out[i4 + 3] = (uint8_t)(v >> 24);
+		}
 }
diff --git a/src/md5/md5_init.c b/src/md5/md5_init.c
index 833dedf..c7ad15f 100644
--- a/src/md5/md5_init.c
+++ b/src/md5/md5_init.c
@@ -1,6 +1,13 @@
-#include "compiler.h"
 #include "md5.h"
 
-void	md5_init(__unused void *ctx)
+void	md5_init(void *ctx)
 {
+	struct md5_ctx	*local_ctx = ctx;
+
+	local_ctx->state[0] = 0x67452301;
+	local_ctx->state[1] = 0xEFCDAB89;
+	local_ctx->state[2] = 0x98BADCFE;
+	local_ctx->state[3] = 0x10325476;
+
+	local_ctx->count = 0;
 }
diff --git a/src/md5/md5_update.c b/src/md5/md5_update.c
index e2914f2..d619798 100644
--- a/src/md5/md5_update.c
+++ b/src/md5/md5_update.c
@@ -1,7 +1,19 @@
-#include "compiler.h"
 #include "md5.h"
+#include "md5_internal.h"
+#include <stddef.h>
+#include <stdint.h>
 
-void	md5_update(__unused void *ctx, __unused const uint8_t *data,
-		__unused size_t len)
+void	md5_update(void *ctx, const uint8_t *data, size_t len)
 {
+	struct md5_ctx	*local_ctx = ctx;
+
+
+	for (size_t i = 0; i < len; ++i)
+	{
+		local_ctx->buf[(local_ctx->count & 63)] = data[i];
+		++local_ctx->count;
+		if (0 == (local_ctx->count & 63))
+			md5_compress(local_ctx, local_ctx->buf);
+	}
+
 }