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diff --git a/src/lib/rng/chacha_rng/chacha_rng.h b/src/lib/rng/chacha_rng/chacha_rng.h
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+++ b/src/lib/rng/chacha_rng/chacha_rng.h
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+/*
+* ChaCha_RNG
+* (C) 2017 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_CHACHA_RNG_H__
+#define BOTAN_CHACHA_RNG_H__
+
+#include <botan/stateful_rng.h>
+#include <botan/stream_cipher.h>
+#include <botan/mac.h>
+
+namespace Botan {
+
+class Entropy_Sources;
+
+/**
+* ChaCha_RNG is a very fast but completely ad-hoc RNG created by
+* creating a 256-bit random value and using it as a key for ChaCha20.
+*
+* The RNG maintains two 256-bit keys, one for HMAC_SHA256 (HK) and the
+* other for ChaCha20 (CK). To compute a new key in response to
+* reseeding request or add_entropy calls, ChaCha_RNG computes
+*   CK' = HMAC_SHA256(HK, input_material)
+* Then a new HK' is computed by running ChaCha20 with the new key to
+* output 32 bytes:
+*   HK' = ChaCha20(CK')
+*
+* Now output can be produced by continuing to produce output with ChaCha20
+* under CK'
+*
+* The first HK (before seeding occurs) is taken as the all zero value.
+*
+* @warning This RNG construction is probably fine but is non-standard.
+* The primary reason to use it is in cases where the other RNGs are
+* not fast enough.
+*/
+class BOTAN_DLL ChaCha_RNG final : public Stateful_RNG
+   {
+   public:
+      /**
+      * Automatic reseeding is disabled completely, as it has no access to
+      * any source for seed material.
+      *
+      * If a fork is detected, the RNG will be unable to reseed itself
+      * in response. In this case, an exception will be thrown rather
+      * than generating duplicated output.
+      */
+      ChaCha_RNG();
+
+      /**
+      * Provide an initial seed to the RNG, without providing an
+      * underlying RNG or entropy source. Automatic reseeding is
+      * disabled completely, as it has no access to any source for
+      * seed material.
+      *
+      * If a fork is detected, the RNG will be unable to reseed itself
+      * in response. In this case, an exception will be thrown rather
+      * than generating duplicated output.
+      *
+      * @param seed the seed material, should be at least 256 bits
+      */
+      ChaCha_RNG(const secure_vector<uint8_t>& seed);
+
+      /**
+      * Automatic reseeding from @p underlying_rng will take place after
+      * @p reseed_interval many requests or after a fork was detected.
+      *
+      * @param underlying_rng is a reference to some RNG which will be used
+      * to perform the periodic reseeding
+      * @param reseed_interval specifies a limit of how many times
+      * the RNG will be called before automatic reseeding is performed
+      */
+      ChaCha_RNG(RandomNumberGenerator& underlying_rng,
+                 size_t reseed_interval = BOTAN_RNG_DEFAULT_RESEED_INTERVAL);
+
+      /**
+      * Automatic reseeding from @p entropy_sources will take place after
+      * @p reseed_interval many requests or after a fork was detected.
+      *
+      * @param entropy_sources will be polled to perform reseeding periodically
+      * @param reseed_interval specifies a limit of how many times
+      * the RNG will be called before automatic reseeding is performed.
+      */
+      ChaCha_RNG(Entropy_Sources& entropy_sources,
+                 size_t reseed_interval = BOTAN_RNG_DEFAULT_RESEED_INTERVAL);
+
+      /**
+      * Automatic reseeding from @p underlying_rng and @p entropy_sources
+      * will take place after @p reseed_interval many requests or after
+      * a fork was detected.
+      *
+      * @param underlying_rng is a reference to some RNG which will be used
+      * to perform the periodic reseeding
+      * @param entropy_sources will be polled to perform reseeding periodically
+      * @param reseed_interval specifies a limit of how many times
+      * the RNG will be called before automatic reseeding is performed.
+      */
+      ChaCha_RNG(RandomNumberGenerator& underlying_rng,
+                 Entropy_Sources& entropy_sources,
+                 size_t reseed_interval = BOTAN_RNG_DEFAULT_RESEED_INTERVAL);
+
+      std::string name() const override { return "ChaCha_RNG"; }
+
+      void clear() override;
+
+      void randomize(uint8_t output[], size_t output_len) override;
+
+      void randomize_with_input(uint8_t output[], size_t output_len,
+                                const uint8_t input[], size_t input_len) override;
+
+      void add_entropy(const uint8_t input[], size_t input_len) override;
+
+      size_t security_level() const override;
+
+   private:
+      void update(const uint8_t input[], size_t input_len);
+
+      std::unique_ptr<MessageAuthenticationCode> m_hmac;
+      std::unique_ptr<StreamCipher> m_chacha;
+   };
+
+}
+
+#endif