Move stuff related to generators to src/gen.

2 files changed, 103 insertions, 0 deletions

diff --git a/src/util/random.c b/src/util/random.c
new file mode 100644
index 0000000..519ce6b
--- /dev/null
+++ b/src/util/random.c
@@ -0,0 +1,64 @@
+/*
+ * ecgen, tool for generating Elliptic curve domain parameters
+ * Copyright (C) 2017 J08nY
+ */
+#define _POSIX_C_SOURCE 200809L
+
+#include "random.h"
+#include <time.h>
+
+bool random_init(void) {
+	pari_ulong seed = 0;
+	// Try urandom first
+	FILE *rand = fopen("/dev/urandom", "rb");
+	if (rand) {
+		size_t read = 0;
+		while (read < sizeof(pari_ulong)) {
+			read += fread(&seed + read, 1, sizeof(pari_ulong) - read, rand);
+		}
+
+		fclose(rand);
+	}
+	// Try worse methods later
+	if (seed == 0) {
+		struct timespec t;
+		if (!clock_gettime(CLOCK_REALTIME, &t)) {
+			seed = (pari_ulong)t.tv_nsec;
+		} else {
+			seed = (pari_ulong)time(NULL);
+		}
+	}
+
+	pari_sp ltop = avma;
+	setrand(utoi(seed));
+	avma = ltop;
+
+	return true;
+}
+
+GEN random_prime(unsigned long bits) {
+	pari_sp ltop = avma;
+
+	GEN range = gtovec0(gen_0, 2);
+	gel(range, 1) = powis(gen_2, bits - 1);
+	gel(range, 2) = powis(gen_2, bits);
+
+	GEN p;
+	pari_sp btop = avma;
+	do {
+		p = randomprime(range);
+		p = gerepileupto(btop, p);
+	} while (!isprime(p));
+
+	return gerepilecopy(ltop, p);
+}
+
+GEN random_int(unsigned long bits) {
+	pari_sp ltop = avma;
+
+	GEN range = gtovec0(gen_0, 2);
+	gel(range, 1) = powis(gen_2, bits - 1);
+	gel(range, 2) = powis(gen_2, bits);
+
+	return gerepilecopy(ltop, genrand(range));
+}
diff --git a/src/util/random.h b/src/util/random.h
new file mode 100644
index 0000000..96eb210
--- /dev/null
+++ b/src/util/random.h
@@ -0,0 +1,39 @@
+/*
+ * ecgen, tool for generating Elliptic curve domain parameters
+ * Copyright (C) 2017 J08nY
+ */
+/**
+ * @file random.h
+ */
+#ifndef ECGEN_RANDOM_H
+#define ECGEN_RANDOM_H
+
+#include <pari/pari.h>
+#include <stdbool.h>
+
+/**
+ * @brief Init the PARI-GP random generator.
+ *
+ * Initializes the PARI-GP random generator, tries to do so from
+ * cryptographically strong sources(/dev/urandom) at first but falls back on
+ * clock_gettime and time(NULL).
+ *
+ * @return whether the initialization was successful
+ */
+bool random_init(void);
+
+/**
+ * @brief Generate random <code>bits</code> sized prime.
+ * @param bits the size of the prime to generate
+ * @return a random prime in range [2^(bits - 1), 2^bits]
+ */
+GEN random_prime(unsigned long bits);
+
+/**
+ * @brief Generate random <code>bits</code> sized integer.
+ * @param bits the size of the integer to generate
+ * @return a random integer in range [2^(bits - 1), 2^bits]
+ */
+GEN random_int(unsigned long bits);
+
+#endif  // ECGEN_RANDOM_H