[Cryptech-Commits] [sw/cryptlib] 01/01: Remove cryptech_novena_i2c_entropy, which was an attractive nuisance. Add cryptech_novena_i2c_trng, now that we know what the TRNG I2C interface will be.

[git at cryptech.is]

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sra at hactrn.net pushed a commit to branch master
in repository sw/cryptlib.

commit 2b5383ad73f56652f6e994de3fb611ef2ccaef97
Author: Rob Austein <sra at hactrn.net>
Date:   Fri Dec 5 15:30:19 2014 +0100

    Remove cryptech_novena_i2c_entropy, which was an attractive nuisance.
    Add cryptech_novena_i2c_trng, now that we know what the TRNG I2C
    interface will be.
---
 ...na_i2c_entropy.c => cryptech_novena_i2c_trng.c} | 39 +++++++++++++---------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/src/cryptech_novena_i2c_entropy.c b/src/cryptech_novena_i2c_trng.c
similarity index 92%
rename from src/cryptech_novena_i2c_entropy.c
rename to src/cryptech_novena_i2c_trng.c
index b2e6e22..599c0db 100644
--- a/src/cryptech_novena_i2c_entropy.c
+++ b/src/cryptech_novena_i2c_trng.c
@@ -1,11 +1,11 @@
 /* 
- * cryptech_novena_i2c_entropy.c
+ * cryptech_novena_i2c_trng.c
  * ------------------------------
  *
  * This is an early prototype Hardware Adaption Layer (HAL) for using
  * Cryptlib with the Cryptech project's FGPA cores over an I2C bus on
  * the Novena PVT1 development board using the "coretest" byte stream
- * protocol.  This is compatible with the test/novena_entropy FPGA build.
+ * protocol.  This is compatible with the test/novena_trng FPGA build.
  *
  * The communication channel used here is not suitable for production
  * use, this is just a prototype.
@@ -111,12 +111,12 @@
 
 /*
  * Address for reading 32 bits of entropy from the noise board.
- * ENTROPY_VALID is nonzero if there's valid entropy available.
+ * TRNG_VALID is nonzero if valid random bits are available.
  */
 
-#define ENTROPY_PREFIX		0x20
-#define	ENTROPY_ADDR		0x20
-#define	ENTROPY_VALID		0x11
+#define	TRNG_PREFIX		0x0b
+#define	TRNG_DATA		0x20
+#define	TRNG_VALID		0x11
 
 static int i2cfd = -1;
 static int debug = 0;
@@ -363,9 +363,14 @@ static int i2c_wait_valid(const unsigned char addr0)
 
 /*
  * First attempt at reading random data from the Novena.
- * Not sure what we should do if ENTROPY_VALID isn't lit, spin wait?
+ *
+ * In theory, we should wait for TRNG_VALID before reading random
+ * data, but as long as this is running over I2C we're going to be so
+ * slow that there's no point, and checking would just make us slower.
  */
 
+#define WAIT_FOR_TRNG_VALID	0
+
 static int readRandom(void *buffer, const int length)
 {
   unsigned char temp[4], *buf = buffer;
@@ -376,23 +381,27 @@ static int readRandom(void *buffer, const int length)
   REQUIRES_B(length >= 1 && length < MAX_INTLENGTH);
 
   for (i = 0; i < length; i += 4) {
-    if (!i2c_wait_valid(ENTROPY_PREFIX)) {
-      fprintf(stderr, "[ i2c_wait_valid(ENTROPY_PREFIX) failed ]\n");
+
+#if WAIT_FOR_TRNG_VALID
+    if (!i2c_wait_valid(TRNG_PREFIX)) {
+      fprintf(stderr, "[ i2c_wait_valid(TRNG_PREFIX) failed ]\n");
       return 0;
     }
     do {
-      if (!i2c_read(ENTROPY_PREFIX, ENTROPY_VALID, temp)) {
-        fprintf(stderr, "[ i2c_read(ENTROPY_VALID) failed ]\n");
+      if (!i2c_read(TRNG_PREFIX, TRNG_VALID, temp)) {
+        fprintf(stderr, "[ i2c_read(TRNG_VALID) failed ]\n");
         return 0;
       }
     } while (!temp[3]);
-    if (!i2c_wait_valid(ENTROPY_PREFIX)) {
-      fprintf(stderr, "[ i2c_wait_valid(ENTROPY_PREFIX) failed ]\n");
+    if (!i2c_wait_valid(TRNG_PREFIX)) {
+      fprintf(stderr, "[ i2c_wait_valid(TRNG_PREFIX) failed ]\n");
       return 0;
     }
+#endif  /* WAIT_FOR_TRNG_VALID */
+
     last = (length - i) < 4;
-    if (!i2c_read(ENTROPY_PREFIX, ENTROPY_ADDR, last ? temp : buf + i)) {
-      fprintf(stderr, "[ i2c_read(ENTROPY_ADDR) failed ]\n");
+    if (!i2c_read(TRNG_PREFIX, TRNG_DATA, (last ? temp : (buf + i)))) {
+      fprintf(stderr, "[ i2c_read(TRNG_DATA) failed ]\n");
       return 0;
     }
     if (last) {