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Diffstat (limited to 'utils/random.c')
| -rw-r--r-- | utils/random.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/utils/random.c b/utils/random.c new file mode 100644 index 0000000..0588c44 --- /dev/null +++ b/utils/random.c @@ -0,0 +1,169 @@ +//*****************************************************************************
+//
+// random.c - Random number generator utilizing MD4 hash function of
+// environmental noise captured as the seed and a linear congruence
+// generator for the random numbers.
+//
+// Copyright (c) 2011-2014 Texas Instruments Incorporated. All rights reserved.
+// Software License Agreement
+//
+// Texas Instruments (TI) is supplying this software for use solely and
+// exclusively on TI's microcontroller products. The software is owned by
+// TI and/or its suppliers, and is protected under applicable copyright
+// laws. You may not combine this software with "viral" open-source
+// software in order to form a larger program.
+//
+// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
+// NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
+// NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
+// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
+// DAMAGES, FOR ANY REASON WHATSOEVER.
+//
+// This is part of revision 2.1.0.12573 of the Tiva Utility Library.
+//
+//*****************************************************************************
+
+#include <stdint.h>
+#include "ustdlib.h"
+#include "random.h"
+
+//*****************************************************************************
+//
+//! \addtogroup random_api
+//! @{
+//
+//*****************************************************************************
+
+//*****************************************************************************
+//
+// The pool of entropy that has been collected.
+//
+//*****************************************************************************
+static uint32_t g_pui32RandomEntropy[16];
+
+//*****************************************************************************
+//
+// The index of the next byte to be added to the entropy pool.
+//
+//*****************************************************************************
+static uint32_t g_ui32RandomIndex = 0;
+
+//*****************************************************************************
+//
+//! Add entropy to the pool.
+//!
+//! \param ui32Entropy is an 8-bit value that is added to the entropy pool
+//!
+//! This function allows the user application code to add entropy (random data)
+//! to the pool at any time.
+//!
+//! \return None
+//
+//*****************************************************************************
+void
+RandomAddEntropy(uint32_t ui32Entropy)
+{
+ //
+ // Add this byte to the entropy pool.
+ //
+ ((uint8_t *)g_pui32RandomEntropy)[g_ui32RandomIndex] = ui32Entropy & 0xff;
+
+ //
+ // Increment to the next byte of the entropy pool.
+ //
+ g_ui32RandomIndex = (g_ui32RandomIndex + 1) & 63;
+}
+
+//*****************************************************************************
+//
+//! Set the random number generator seed.
+//!
+//! Seed the random number generator by running a MD4 hash on the entropy pool.
+//! Note that the entropy pool may change from beneath us, but for the purposes
+//! of generating random numbers that is not a concern. Also, the MD4 hash was
+//! broken long ago, but since it is being used to generate random numbers
+//! instead of providing security this is not a concern.
+//!
+//! \return New seed value.
+//
+//*****************************************************************************
+uint32_t
+RandomSeed(void)
+{
+ uint32_t ui32A, ui32B, ui32C, ui32D, ui32Temp, ui32Idx;
+
+ //
+ // Initialize the digest.
+ //
+ ui32A = 0x67452301;
+ ui32B = 0xefcdab89;
+ ui32C = 0x98badcfe;
+ ui32D = 0x10325476;
+
+ //
+ // Perform the first round of operations.
+ //
+#define F(a, b, c, d, k, s) \
+ { \
+ ui32Temp = a + (d ^ (b & (c ^ d))) + g_pui32RandomEntropy[k]; \
+ a = (ui32Temp << s) | (ui32Temp >> (32 - s)); \
+ }
+ for(ui32Idx = 0; ui32Idx < 16; ui32Idx += 4)
+ {
+ F(ui32A, ui32B, ui32C, ui32D, ui32Idx + 0, 3);
+ F(ui32D, ui32A, ui32B, ui32C, ui32Idx + 1, 7);
+ F(ui32C, ui32D, ui32A, ui32B, ui32Idx + 2, 11);
+ F(ui32B, ui32C, ui32D, ui32A, ui32Idx + 3, 19);
+ }
+
+ //
+ // Perform the second round of operations.
+ //
+#define G(a, b, c, d, k, s) \
+ { \
+ ui32Temp = (a + ((b & c) | (b & d) | (c & d)) + \
+ g_pui32RandomEntropy[k] + 0x5a827999); \
+ a = (ui32Temp << s) | (ui32Temp >> (32 - s)); \
+ }
+ for(ui32Idx = 0; ui32Idx < 4; ui32Idx++)
+ {
+ G(ui32A, ui32B, ui32C, ui32D, ui32Idx + 0, 3);
+ G(ui32D, ui32A, ui32B, ui32C, ui32Idx + 4, 5);
+ G(ui32C, ui32D, ui32A, ui32B, ui32Idx + 8, 9);
+ G(ui32B, ui32C, ui32D, ui32A, ui32Idx + 12, 13);
+ }
+
+ //
+ // Perform the third round of operations.
+ //
+#define H(a, b, c, d, k, s) \
+ { \
+ ui32Temp = a + (b ^ c ^ d) + g_pui32RandomEntropy[k] + 0x6ed9eba1; \
+ a = (ui32Temp << s) | (ui32Temp >> (32 - s)); \
+ }
+ for(ui32Idx = 0; ui32Idx < 4; ui32Idx += 2)
+ {
+ H(ui32A, ui32B, ui32C, ui32D, ui32Idx + 0, 3);
+ H(ui32D, ui32A, ui32B, ui32C, ui32Idx + 8, 9);
+ H(ui32C, ui32D, ui32A, ui32B, ui32Idx + 4, 11);
+ H(ui32B, ui32C, ui32D, ui32A, ui32Idx + 12, 15);
+
+ if(ui32Idx == 2)
+ {
+ ui32Idx -= 3;
+ }
+ }
+
+ //
+ // Use the first word of the resulting digest as the random number seed.
+ //
+ return(ui32A + 0x67452301);
+}
+
+//*****************************************************************************
+//
+// Close the Doxygen group.
+//! @}
+//
+//*****************************************************************************
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