#include "MD5.h"
#include "mbedtls/base64.h"
const byte md5Len = 16; // 16 bytes hash
const byte b64Len = ((md5Len + 2) / 3) * 4 + 1; // max length for the base64 encode

void setup() {
  Serial.begin(115200);
  //generate the MD5 hash for our string
  unsigned char* hash = MD5::make_hash("Hello World");  // 128 bits hash = 16 bytes

  Serial.print("Hash = ");
  for (byte i = 0; i < md5Len; i++) {
    if (hash[i] < 0x10) Serial.write('0');
    Serial.print(hash[i], HEX);
    Serial.write(' ');
  }
  Serial.println();

  unsigned char b64Out[b64Len];
  size_t b64OutLen;
  mbedtls_base64_encode(b64Out, b64Len, &b64OutLen, hash, md5Len);
  Serial.print("Base64 = ");
  Serial.println((char*) b64Out);
  free(hash);
}

void loop() {}


sketch.ino

diagram.json

#include "MD5.h"

MD5::MD5()
{
	//nothing
	return;
}

char* MD5::make_digest(const unsigned char *digest, int len) /* {{{ */
{
	char * md5str = (char*) malloc(sizeof(char)*(len*2+1));
	static const char hexits[17] = "0123456789abcdef";
	int i;

	for (i = 0; i < len; i++) {
		md5str[i * 2]       = hexits[digest[i] >> 4];
		md5str[(i * 2) + 1] = hexits[digest[i] &  0x0F];
	}
	md5str[len * 2] = '\0';
	return md5str;
}

/*
 * The basic MD5 functions.
 *
 * E and G are optimized compared to their RFC 1321 definitions for
 * architectures that lack an AND-NOT instruction, just like in Colin Plumb's
 * implementation.
 * E() has been used instead of F() because F() is already defined in the Arduino core
 */
#define E(x, y, z)			((z) ^ ((x) & ((y) ^ (z))))
#define G(x, y, z)			((y) ^ ((z) & ((x) ^ (y))))
#define H(x, y, z)			((x) ^ (y) ^ (z))
#define I(x, y, z)			((y) ^ ((x) | ~(z)))

/*
 * The MD5 transformation for all four rounds.
 */
#define STEP(f, a, b, c, d, x, t, s) \
	(a) += f((b), (c), (d)) + (x) + (t); \
	(a) = (((a) << (s)) | (((a) & 0xffffffff) >> (32 - (s)))); \
	(a) += (b);

/*
 * SET reads 4 input bytes in little-endian byte order and stores them
 * in a properly aligned word in host byte order.
 *
 * The check for little-endian architectures that tolerate unaligned
 * memory accesses is just an optimization.  Nothing will break if it
 * doesn't work.
 */
#if defined(__i386__) || defined(__x86_64__) || defined(__vax__)
# define SET(n) \
	(*(MD5_u32plus *)&ptr[(n) * 4])
# define GET(n) \
	SET(n)
#else
# define SET(n) \
	(ctx->block[(n)] = \
	(MD5_u32plus)ptr[(n) * 4] | \
	((MD5_u32plus)ptr[(n) * 4 + 1] << 8) | \
	((MD5_u32plus)ptr[(n) * 4 + 2] << 16) | \
	((MD5_u32plus)ptr[(n) * 4 + 3] << 24))
# define GET(n) \
	(ctx->block[(n)])
#endif

/*
 * This processes one or more 64-byte data blocks, but does NOT update
 * the bit counters.  There are no alignment requirements.
 */
const void *MD5::body(void *ctxBuf, const void *data, size_t size)
{
	MD5_CTX *ctx = (MD5_CTX*)ctxBuf;
	const unsigned char *ptr;
	MD5_u32plus a, b, c, d;
	MD5_u32plus saved_a, saved_b, saved_c, saved_d;

	ptr = (unsigned char*)data;

	a = ctx->a;
	b = ctx->b;
	c = ctx->c;
	d = ctx->d;

	do {
		saved_a = a;
		saved_b = b;
		saved_c = c;
		saved_d = d;

/* Round 1
 * E() has been used instead of F() because F() is already defined in the Arduino core
 */
		STEP(E, a, b, c, d, SET(0), 0xd76aa478, 7)
		STEP(E, d, a, b, c, SET(1), 0xe8c7b756, 12)
		STEP(E, c, d, a, b, SET(2), 0x242070db, 17)
		STEP(E, b, c, d, a, SET(3), 0xc1bdceee, 22)
		STEP(E, a, b, c, d, SET(4), 0xf57c0faf, 7)
		STEP(E, d, a, b, c, SET(5), 0x4787c62a, 12)
		STEP(E, c, d, a, b, SET(6), 0xa8304613, 17)
		STEP(E, b, c, d, a, SET(7), 0xfd469501, 22)
		STEP(E, a, b, c, d, SET(8), 0x698098d8, 7)
		STEP(E, d, a, b, c, SET(9), 0x8b44f7af, 12)
		STEP(E, c, d, a, b, SET(10), 0xffff5bb1, 17)
		STEP(E, b, c, d, a, SET(11), 0x895cd7be, 22)
		STEP(E, a, b, c, d, SET(12), 0x6b901122, 7)
		STEP(E, d, a, b, c, SET(13), 0xfd987193, 12)
		STEP(E, c, d, a, b, SET(14), 0xa679438e, 17)
		STEP(E, b, c, d, a, SET(15), 0x49b40821, 22)

/* Round 2 */
		STEP(G, a, b, c, d, GET(1), 0xf61e2562, 5)
		STEP(G, d, a, b, c, GET(6), 0xc040b340, 9)
		STEP(G, c, d, a, b, GET(11), 0x265e5a51, 14)
		STEP(G, b, c, d, a, GET(0), 0xe9b6c7aa, 20)
		STEP(G, a, b, c, d, GET(5), 0xd62f105d, 5)
		STEP(G, d, a, b, c, GET(10), 0x02441453, 9)
		STEP(G, c, d, a, b, GET(15), 0xd8a1e681, 14)
		STEP(G, b, c, d, a, GET(4), 0xe7d3fbc8, 20)
		STEP(G, a, b, c, d, GET(9), 0x21e1cde6, 5)
		STEP(G, d, a, b, c, GET(14), 0xc33707d6, 9)
		STEP(G, c, d, a, b, GET(3), 0xf4d50d87, 14)
		STEP(G, b, c, d, a, GET(8), 0x455a14ed, 20)
		STEP(G, a, b, c, d, GET(13), 0xa9e3e905, 5)
		STEP(G, d, a, b, c, GET(2), 0xfcefa3f8, 9)
		STEP(G, c, d, a, b, GET(7), 0x676f02d9, 14)
		STEP(G, b, c, d, a, GET(12), 0x8d2a4c8a, 20)

/* Round 3 */
		STEP(H, a, b, c, d, GET(5), 0xfffa3942, 4)
		STEP(H, d, a, b, c, GET(8), 0x8771f681, 11)
		STEP(H, c, d, a, b, GET(11), 0x6d9d6122, 16)
		STEP(H, b, c, d, a, GET(14), 0xfde5380c, 23)
		STEP(H, a, b, c, d, GET(1), 0xa4beea44, 4)
		STEP(H, d, a, b, c, GET(4), 0x4bdecfa9, 11)
		STEP(H, c, d, a, b, GET(7), 0xf6bb4b60, 16)
		STEP(H, b, c, d, a, GET(10), 0xbebfbc70, 23)
		STEP(H, a, b, c, d, GET(13), 0x289b7ec6, 4)
		STEP(H, d, a, b, c, GET(0), 0xeaa127fa, 11)
		STEP(H, c, d, a, b, GET(3), 0xd4ef3085, 16)
		STEP(H, b, c, d, a, GET(6), 0x04881d05, 23)
		STEP(H, a, b, c, d, GET(9), 0xd9d4d039, 4)
		STEP(H, d, a, b, c, GET(12), 0xe6db99e5, 11)
		STEP(H, c, d, a, b, GET(15), 0x1fa27cf8, 16)
		STEP(H, b, c, d, a, GET(2), 0xc4ac5665, 23)

/* Round 4 */
		STEP(I, a, b, c, d, GET(0), 0xf4292244, 6)
		STEP(I, d, a, b, c, GET(7), 0x432aff97, 10)
		STEP(I, c, d, a, b, GET(14), 0xab9423a7, 15)
		STEP(I, b, c, d, a, GET(5), 0xfc93a039, 21)
		STEP(I, a, b, c, d, GET(12), 0x655b59c3, 6)
		STEP(I, d, a, b, c, GET(3), 0x8f0ccc92, 10)
		STEP(I, c, d, a, b, GET(10), 0xffeff47d, 15)
		STEP(I, b, c, d, a, GET(1), 0x85845dd1, 21)
		STEP(I, a, b, c, d, GET(8), 0x6fa87e4f, 6)
		STEP(I, d, a, b, c, GET(15), 0xfe2ce6e0, 10)
		STEP(I, c, d, a, b, GET(6), 0xa3014314, 15)
		STEP(I, b, c, d, a, GET(13), 0x4e0811a1, 21)
		STEP(I, a, b, c, d, GET(4), 0xf7537e82, 6)
		STEP(I, d, a, b, c, GET(11), 0xbd3af235, 10)
		STEP(I, c, d, a, b, GET(2), 0x2ad7d2bb, 15)
		STEP(I, b, c, d, a, GET(9), 0xeb86d391, 21)

		a += saved_a;
		b += saved_b;
		c += saved_c;
		d += saved_d;

		ptr += 64;
	} while (size -= 64);

	ctx->a = a;
	ctx->b = b;
	ctx->c = c;
	ctx->d = d;

	return ptr;
}

void MD5::MD5Init(void *ctxBuf)
{
	MD5_CTX *ctx = (MD5_CTX*)ctxBuf;
	ctx->a = 0x67452301;
	ctx->b = 0xefcdab89;
	ctx->c = 0x98badcfe;
	ctx->d = 0x10325476;

	ctx->lo = 0;
	ctx->hi = 0;

    memset(ctx->block, 0, sizeof(ctx->block));
    memset(ctx->buffer, 0, sizeof(ctx->buffer));
}

void MD5::MD5Update(void *ctxBuf, const void *data, size_t size)
{
	MD5_CTX *ctx = (MD5_CTX*)ctxBuf;
	MD5_u32plus saved_lo;
	MD5_u32plus used, free;

	saved_lo = ctx->lo;
	if ((ctx->lo = (saved_lo + size) & 0x1fffffff) < saved_lo) {
		ctx->hi++;
	}
	ctx->hi += size >> 29;

	used = saved_lo & 0x3f;

	if (used) {
		free = 64 - used;

		if (size < free) {
			memcpy(&ctx->buffer[used], data, size);
			return;
		}

		memcpy(&ctx->buffer[used], data, free);
		data = (unsigned char *)data + free;
		size -= free;
		body(ctx, ctx->buffer, 64);
	}

	if (size >= 64) {
		data = body(ctx, data, size & ~(size_t)0x3f);
		size &= 0x3f;
	}

	memcpy(ctx->buffer, data, size);
}

void MD5::MD5Final(unsigned char *result, void *ctxBuf)
{
	MD5_CTX *ctx = (MD5_CTX*)ctxBuf;
	MD5_u32plus used, free;

	used = ctx->lo & 0x3f;

	ctx->buffer[used++] = 0x80;

	free = 64 - used;

	if (free < 8) {
		memset(&ctx->buffer[used], 0, free);
		body(ctx, ctx->buffer, 64);
		used = 0;
		free = 64;
	}

	memset(&ctx->buffer[used], 0, free - 8);

	ctx->lo <<= 3;
	ctx->buffer[56] = ctx->lo;
	ctx->buffer[57] = ctx->lo >> 8;
	ctx->buffer[58] = ctx->lo >> 16;
	ctx->buffer[59] = ctx->lo >> 24;
	ctx->buffer[60] = ctx->hi;
	ctx->buffer[61] = ctx->hi >> 8;
	ctx->buffer[62] = ctx->hi >> 16;
	ctx->buffer[63] = ctx->hi >> 24;

	body(ctx, ctx->buffer, 64);

	result[0] = ctx->a;
	result[1] = ctx->a >> 8;
	result[2] = ctx->a >> 16;
	result[3] = ctx->a >> 24;
	result[4] = ctx->b;
	result[5] = ctx->b >> 8;
	result[6] = ctx->b >> 16;
	result[7] = ctx->b >> 24;
	result[8] = ctx->c;
	result[9] = ctx->c >> 8;
	result[10] = ctx->c >> 16;
	result[11] = ctx->c >> 24;
	result[12] = ctx->d;
	result[13] = ctx->d >> 8;
	result[14] = ctx->d >> 16;
	result[15] = ctx->d >> 24;

	memset(ctx, 0, sizeof(*ctx));
}
unsigned char* MD5::make_hash(char *arg)
{
	MD5_CTX context;
	unsigned char * hash = (unsigned char *) malloc(16);
	MD5Init(&context);
	MD5Update(&context, arg, strlen(arg));
	MD5Final(hash, &context);
	return hash;
}
unsigned char* MD5::make_hash(char *arg,size_t size)
{
	MD5_CTX context;
	unsigned char * hash = (unsigned char *) malloc(16);
	MD5Init(&context);
	MD5Update(&context, arg, size);
	MD5Final(hash, &context);
	return hash;
}



MD5.cpp

#ifndef MD5_h
#define MD5_h

#include "Arduino.h"

/*
 * This is an OpenSSL-compatible implementation of the RSA Data Security,
 * Inc. MD5 Message-Digest Algorithm (RFC 1321).
 *
 * Written by Solar Designer <solar at openwall.com> in 2001, and placed
 * in the public domain.  There's absolutely no warranty.
 *
 * This differs from Colin Plumb's older public domain implementation in
 * that no 32-bit integer data type is required, there's no compile-time
 * endianness configuration, and the function prototypes match OpenSSL's.
 * The primary goals are portability and ease of use.
 *
 * This implementation is meant to be fast, but not as fast as possible.
 * Some known optimizations are not included to reduce source code size
 * and avoid compile-time configuration.
 */

/*
 * Updated by Scott MacVicar for arduino
 * <scott@macvicar.net>
 */

#include <string.h>

typedef unsigned long MD5_u32plus;

typedef struct {
	MD5_u32plus lo, hi;
	MD5_u32plus a, b, c, d;
	unsigned char buffer[64];
	MD5_u32plus block[16];
} MD5_CTX;

class MD5
{
public:
	MD5();
	static unsigned char* make_hash(char *arg);
	static unsigned char* make_hash(char *arg,size_t size);
	static char* make_digest(const unsigned char *digest, int len);
 	static const void *body(void *ctxBuf, const void *data, size_t size);
	static void MD5Init(void *ctxBuf);
	static void MD5Final(unsigned char *result, void *ctxBuf);
	static void MD5Update(void *ctxBuf, const void *data, size_t size);
};

#endif