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+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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+ *
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+ * LibTomCrypt is a library that provides various cryptographic
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+ * algorithms in a highly modular and flexible manner.
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+ *
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+ * The library is free for all purposes without any express
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+ * guarantee it works.
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+ */
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+
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+#include "tomcrypt.h"
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+
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+#ifdef LTC_CHACHA
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+
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+const struct ltc_prng_descriptor chacha_prng_desc =
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+{
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+ "chacha",
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+ sizeof(chacha_state),
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+ &chacha_prng_start,
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+ &chacha_prng_add_entropy,
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+ &chacha_prng_ready,
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+ &chacha_prng_read,
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+ &chacha_prng_done,
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+ &chacha_prng_export,
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+ &chacha_prng_import,
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+ &chacha_prng_test
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+};
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+
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+/**
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+ Start the PRNG
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+ @param prng[out] The PRNG state to initialize
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+ @return CRYPT_OK if successful
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+*/
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+int chacha_prng_start(prng_state *prng)
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+{
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+ LTC_ARGCHK(prng != NULL);
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+ prng->chacha.ready = 0;
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+ XMEMSET(&prng->chacha.ent, 0, 40);
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+ prng->chacha.idx = 0;
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+ return CRYPT_OK;
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+}
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+
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+/**
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+ Add entropy to the PRNG state
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+ @param in The data to add
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+ @param inlen Length of the data to add
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+ @param prng PRNG state to update
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+ @return CRYPT_OK if successful
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+*/
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+int chacha_prng_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
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+{
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+ unsigned char buf[40];
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+ unsigned long i;
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+ int err;
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+
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+ LTC_ARGCHK(prng != NULL);
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+ LTC_ARGCHK(in != NULL);
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+ LTC_ARGCHK(inlen > 0);
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+
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+ if (prng->chacha.ready) {
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+ /* chacha_prng_ready() was already called, do "rekey" operation */
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+ if ((err = chacha_keystream(&prng->chacha.s, buf, 40)) != CRYPT_OK) return err;
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+ for(i = 0; i < inlen; i++) buf[i % 40] ^= in[i];
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+ /* key 32 bytes, 20 rounds */
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+ if ((err = chacha_setup(&prng->chacha.s, buf, 32, 20)) != CRYPT_OK) return err;
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+ /* iv 8 bytes */
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+ if ((err = chacha_ivctr64(&prng->chacha.s, buf + 32, 8, 0)) != CRYPT_OK) return err;
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+ }
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+ else {
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+ /* chacha_prng_ready() was not called yet, add entropy to ent buffer */
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+ while (inlen--) prng->chacha.ent[prng->chacha.idx++ % 40] ^= *in++;
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+ }
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+
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+ return CRYPT_OK;
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+}
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+
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+/**
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+ Make the PRNG ready to read from
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+ @param prng The PRNG to make active
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+ @return CRYPT_OK if successful
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+*/
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+int chacha_prng_ready(prng_state *prng)
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+{
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+ int err;
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+
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+ LTC_ARGCHK(prng != NULL);
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+
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+ /* key 32 bytes, 20 rounds */
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+ if ((err = chacha_setup(&prng->chacha.s, prng->chacha.ent, 32, 20)) != CRYPT_OK) return err;
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+ /* iv 8 bytes */
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+ if ((err = chacha_ivctr64(&prng->chacha.s, prng->chacha.ent + 32, 8, 0)) != CRYPT_OK) return err;
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+ XMEMSET(&prng->chacha.ent, 0, 40);
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+ prng->chacha.ready = 1;
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+ prng->chacha.idx = 0;
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+ return CRYPT_OK;
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+}
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+
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+/**
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+ Read from the PRNG
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+ @param out Destination
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+ @param outlen Length of output
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+ @param prng The active PRNG to read from
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+ @return Number of octets read
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+*/
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+unsigned long chacha_prng_read(unsigned char *out, unsigned long outlen, prng_state *prng)
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+{
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+ if (chacha_keystream(&prng->chacha.s, out, outlen) != CRYPT_OK) return 0;
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+ return outlen;
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+}
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+
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+/**
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+ Terminate the PRNG
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+ @param prng The PRNG to terminate
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+ @return CRYPT_OK if successful
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+*/
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+int chacha_prng_done(prng_state *prng)
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+{
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+ LTC_UNUSED_PARAM(prng);
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+ prng->chacha.ready = 0;
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+ XMEMSET(&prng->chacha.s, 0, sizeof(chacha_state));
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+ return CRYPT_OK;
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+}
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+
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+/**
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+ Export the PRNG state
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+ @param out [out] Destination
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+ @param outlen [in/out] Max size and resulting size of the state
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+ @param prng The PRNG to export
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+ @return CRYPT_OK if successful
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+*/
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+int chacha_prng_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
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+{
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+ unsigned long len = sizeof(chacha_state);
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+ LTC_ARGCHK(outlen != NULL);
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+ LTC_ARGCHK(out != NULL);
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+ LTC_ARGCHK(prng != NULL);
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+
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+ if (!prng->chacha.ready) {
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+ return CRYPT_ERROR;
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+ }
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+ if (*outlen < len) {
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+ *outlen = len;
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+ return CRYPT_BUFFER_OVERFLOW;
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+ }
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+ XMEMCPY(out, &prng->chacha.s, len);
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+ *outlen = len;
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+ return CRYPT_OK;
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+}
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+
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+/**
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+ Import a PRNG state
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+ @param in The PRNG state
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+ @param inlen Size of the state
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+ @param prng The PRNG to import
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+ @return CRYPT_OK if successful
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+*/
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+int chacha_prng_import(const unsigned char *in, unsigned long inlen, prng_state *prng)
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+{
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+ unsigned long len = sizeof(chacha_state);
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+ LTC_ARGCHK(in != NULL);
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+ LTC_ARGCHK(prng != NULL);
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+
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+ if (inlen != len) return CRYPT_INVALID_ARG;
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+ XMEMCPY(&prng->chacha.s, in, inlen);
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+ prng->chacha.ready = 1;
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+ return CRYPT_OK;
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+}
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+
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+/**
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+ PRNG self-test
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+ @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
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+*/
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+int chacha_prng_test(void)
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+{
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+#ifndef LTC_TEST
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+ return CRYPT_NOP;
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+#else
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+ prng_state st;
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+ unsigned char en[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a,
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+ 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14,
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+ 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e,
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+ 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
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+ 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32 };
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+ unsigned char dmp[300];
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+ unsigned long dmplen = sizeof(dmp);
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+ unsigned char out[500];
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+ unsigned char t1[] = { 0x59, 0xb2, 0x26, 0x95, 0x2b, 0x01, 0x8f, 0x05, 0xbe, 0xd8 };
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+ unsigned char t2[] = { 0x30, 0x34, 0x5c, 0x6e, 0x56, 0x18, 0x8c, 0x46, 0xbe, 0x8a };
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+
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+ chacha_prng_start(&st);
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+ chacha_prng_add_entropy(en, sizeof(en), &st); /* add entropy to uninitialized prng */
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+ chacha_prng_ready(&st);
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+ chacha_prng_read(out, 10, &st); /* 10 bytes for testing */
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+ if (compare_testvector(out, 10, t1, sizeof(t1), "CHACHA-PRNG", 1) != 0) return CRYPT_FAIL_TESTVECTOR;
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+ chacha_prng_read(out, 500, &st);
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+ chacha_prng_add_entropy(en, sizeof(en), &st); /* add entropy to already initialized prng */
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+ chacha_prng_read(out, 500, &st);
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+ chacha_prng_export(dmp, &dmplen, &st);
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+ chacha_prng_read(out, 500, &st); /* skip 500 bytes */
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+ chacha_prng_read(out, 10, &st); /* 10 bytes for testing */
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+ if (compare_testvector(out, 10, t2, sizeof(t2), "CHACHA-PRNG", 2) != 0) return CRYPT_FAIL_TESTVECTOR;
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+ chacha_prng_done(&st);
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+
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+ XMEMSET(&st, 0xFF, sizeof(st)); /* just to be sure */
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+ chacha_prng_import(dmp, dmplen, &st);
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+ chacha_prng_read(out, 500, &st); /* skip 500 bytes */
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+ chacha_prng_read(out, 10, &st); /* 10 bytes for testing */
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+ if (compare_testvector(out, 10, t2, sizeof(t2), "CHACHA-PRNG", 3) != 0) return CRYPT_FAIL_TESTVECTOR;
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+ chacha_prng_done(&st);
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+
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+ return CRYPT_OK;
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+#endif
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+}
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+
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+#endif
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