Add TEA enc/decryption algorithm.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@794 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/algos/tea.c b/algos/tea.c
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+++ b/algos/tea.c
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+/**
+ * \file
+ * <!--
+ * Copyright 2006 Develer S.r.l. (http://www.develer.com/)
+ * This file is part of DevLib - See README.devlib for information.
+ * -->
+ *
+ * \brief TEA Tiny Encription Algorith functions (implementation).
+ *
+ * \version $Id$
+ * \author Francesco Sacchi <batt@develer.com>
+ *
+ * The Tiny Encryption Algorithm (TEA) by David Wheeler and Roger Needham
+ * of the Cambridge Computer Laboratory
+ *
+ * Placed in the Public Domain by David Wheeler and Roger Needham.
+ *
+ * **** ANSI C VERSION ****
+ *
+ * Notes:
+ *
+ * TEA is a Feistel cipher with XOR and and addition as the non-linear
+ * mixing functions.
+ *
+ * Takes 64 bits of data in v[0] and v[1].  Returns 64 bits of data in w[0]
+ * and w[1].  Takes 128 bits of key in k[0] - k[3].
+ *
+ * TEA can be operated in any of the modes of DES. Cipher Block Chaining is,
+ * for example, simple to implement.
+ *
+ * n is the number of iterations. 32 is ample, 16 is sufficient, as few
+ * as eight may be OK.  The algorithm achieves good dispersion after six
+ * iterations. The iteration count can be made variable if required.
+ *
+ * Note this is optimised for 32-bit CPUs with fast shift capabilities. It
+ * can very easily be ported to assembly language on most CPUs.
+ *
+ * delta is chosen to be the real part of (the golden ratio Sqrt(5/4) -
+ * 1/2 ~ 0.618034 multiplied by 2^32).
+ */
+
+/*#*
+ *#* $Log$
+ *#* Revision 1.1  2007/06/07 09:13:40  batt
+ *#* Add TEA enc/decryption algorithm.
+ *#*
+ *#* Revision 1.1  2007/01/10 17:30:10  batt
+ *#* Add cryptographic routines.
+ *#*
+ *#*/
+
+#include "tea.h"
+#include <mware/byteorder.h>
+
+static uint32_t tea_func(uint32_t *in, uint32_t *sum, uint32_t *k)
+{
+       return ((*in << 4) + cpu_to_le32(k[0])) ^ (*in + *sum) ^ ((*in >> 5) + cpu_to_le32(k[1]));
+}
+
+/**
+ * \brief TEA encryption function.
+ * This function encrypts <EM>v</EM> with <EM>k</EM> and returns the
+ * encrypted data in <EM>v</EM>.
+ * \param v Array of two long values containing the data block.
+ * \param k Array of four long values containing the key.
+ */
+void tea_enc(void *_v, void *_k)
+{
+       uint32_t y, z;
+       uint32_t sum = 0;
+       uint8_t n = ROUNDS;
+       uint32_t *v = (uint32_t *)_v;
+       uint32_t *k = (uint32_t *)_k;
+
+       y=cpu_to_le32(v[0]);
+       z=cpu_to_le32(v[1]);
+
+       while(n-- > 0)
+       {
+               sum += DELTA;
+               y += tea_func(&z, &sum, &(k[0]));
+               z += tea_func(&y, &sum, &(k[2]));
+       }
+
+       v[0] = le32_to_cpu(y);
+       v[1] = le32_to_cpu(z);
+}
+
+/**
+ * \brief TEA decryption function.
+ * This function decrypts <EM>v</EM> with <EM>k</EM> and returns the
+ * decrypted data in <EM>v</EM>.
+ * \param v Array of two long values containing the data block.
+ *\param k Array of four long values containing the key.
+ */
+void tea_dec(void *_v, void *_k)
+{
+       uint32_t y, z;
+       uint32_t sum = DELTA * ROUNDS;
+       uint8_t n = ROUNDS;
+       uint32_t *v = (uint32_t *)_v;
+       uint32_t *k = (uint32_t *)_k;
+
+       y = cpu_to_le32(v[0]);
+       z = cpu_to_le32(v[1]);
+
+       while(n-- > 0)
+       {
+               z -= tea_func(&y, &sum, &(k[2]));
+               y -= tea_func(&z, &sum, &(k[0]));
+               sum -= DELTA;
+       }
+
+       v[0] = le32_to_cpu(y);
+       v[1] = le32_to_cpu(z);
+}
+

diff --git a/algos/tea.h b/algos/tea.h
new file mode 100755 (executable)
index 0000000..97803b9
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+++ b/algos/tea.h
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+/**
+ * \file
+ * <!--
+ * Copyright 2006 Develer S.r.l. (http://www.develer.com/)
+ * This file is part of DevLib - See README.devlib for information.
+ * -->
+ *
+ * \brief TEA Tiny Encription Algorith functions (interface).
+ *
+ * \version $Id$
+ * \author Francesco Sacchi <batt@develer.com>
+ *
+ * Documentation for TEA is available at
+ * http://www.cl.cam.ac.uk/ftp/users/djw3/tea.ps.
+ */
+
+#ifndef ALGOS_TEA_H
+#define ALGOS_TEA_H
+
+#include <cfg/compiler.h>
+
+#define TEA_KEY_LEN     16     //!< TEA key size.
+#define TEA_BLOCK_LEN   8      //!< TEA block length.
+
+#define DELTA   0x9E3779B9     //!< Magic value. (Golden number * 2^31)
+#define ROUNDS  32             //!< Number of rounds.
+
+void tea_enc(void *_v, void *_k);
+void tea_dec(void *_v, void *_k);
+
+#endif /* ALGOS_TEA_H */
+