Added XTEA and Pearson Hashing.

Improved message encryption for RF24.

drivers/XTEA/XTEA.cpp

@@ -0,0 +1,82 @@
+
+#include <string.h>
+#include "XTEA.h"
+
+
+
+void XTEA::setKey(void* key) {
+	memcpy(_key, key, 16);
+}
+
+
+void XTEA::setIV(void* iv) {
+	memcpy(_vector, iv, 8);
+}
+
+
+void XTEA::setIV(uint32_t ivh = 0, uint32_t ivl = 0) {
+	memcpy(_vector, &ivh, 4);
+	memcpy(_vector+4, &ivl, 4);
+}
+
+
+void XTEA::cbc_encrypt(void *dest, const void *plain, uint16_t nr_blocks) {
+	for (uint32_t i = 0; i < nr_blocks; i++) {
+
+		// XOR the current vector with the block before encrypting
+		for (auto j = 0; j < 8; j++) {
+			((uint8_t*)plain)[i*8 + j] ^= _vector[j];
+		}
+
+		// Encrypt the block
+		encrypt_block((uint8_t*)dest + i*8, (uint8_t*)plain + i*8);
+
+		// Copy the cipher output to the current vector
+		memcpy(_vector, (uint8_t*)dest + i*8, 8);
+	}
+}
+
+
+void XTEA::cbc_decrypt(void *dest, const void *cipher, uint16_t nr_blocks) {
+	for (uint32_t i = 0; i < nr_blocks; i++) {
+
+		// Decrypt the block
+		decrypt_block((uint8_t*)dest + i*8, (uint8_t*)cipher + i*8);
+
+		// XOR the output with the current vector to fully decrypt
+		for (auto j = 0; j < 8; j++) {
+			((uint8_t*)dest)[i*8 + j] ^= _vector[j];
+		}
+
+		// Copy the cipher text to the current vector
+		memcpy(_vector, (uint8_t*)cipher + i*8, 8);
+	}
+}
+
+
+void XTEA::encrypt_block(void *dest, const void *block) {
+	uint8_t i;
+	uint32_t v0=((uint32_t*)block)[0], v1=((uint32_t*)block)[1];
+	uint32_t sum=0, delta=0x9E3779B9;
+	for(i=0; i<XTEA_CYCLES; i++) {
+		v0 += ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + ((uint32_t*)_key)[sum & 3]);
+		sum += delta;
+		v1 += ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + ((uint32_t*)_key)[sum>>11 & 3]);
+	}
+	((uint32_t*)dest)[0]=v0; ((uint32_t*)dest)[1]=v1;
+}
+
+
+void XTEA::decrypt_block(void *dest, const void *block) {
+	uint8_t i;
+	uint32_t v0=((uint32_t*)block)[0], v1=((uint32_t*)block)[1];
+	uint32_t delta=0x9E3779B9, sum=delta*XTEA_CYCLES;
+	for(i=0; i<XTEA_CYCLES; i++) {
+		v1 -= ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + ((uint32_t*)_key)[sum>>11 & 3]);
+		sum -= delta;
+		v0 -= ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + ((uint32_t*)_key)[sum & 3]);
+	}
+	((uint32_t*)dest)[0]=v0; ((uint32_t*)dest)[1]=v1;
+}
+
+