1 files changed, 43 insertions, 0 deletions
diff --git a/include/crypto/chacha.h b/include/crypto/chacha.h
new file mode 100644
index 0000000000..d29998ffe4
--- /dev/null
+++ b/include/crypto/chacha.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2015-2021 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#ifndef OSSL_CRYPTO_CHACHA_H
+#define OSSL_CRYPTO_CHACHA_H
+# pragma once
+
+#include <stddef.h>
+
+/*
+ * ChaCha20_ctr32 encrypts |len| bytes from |inp| with the given key and
+ * nonce and writes the result to |out|, which may be equal to |inp|.
+ * The |key| is not 32 bytes of verbatim key material though, but the
+ * said material collected into 8 32-bit elements array in host byte
+ * order. Same approach applies to nonce: the |counter| argument is
+ * pointer to concatenated nonce and counter values collected into 4
+ * 32-bit elements. This, passing crypto material collected into 32-bit
+ * elements as opposite to passing verbatim byte vectors, is chosen for
+ * efficiency in multi-call scenarios.
+ */
+void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,
+                    size_t len, const unsigned int key[8],
+                    const unsigned int counter[4]);
+/*
+ * You can notice that there is no key setup procedure. Because it's
+ * as trivial as collecting bytes into 32-bit elements, it's reckoned
+ * that below macro is sufficient.
+ */
+#define CHACHA_U8TOU32(p)  ( \
+                ((unsigned int)(p)[0])     | ((unsigned int)(p)[1]<<8) | \
+                ((unsigned int)(p)[2]<<16) | ((unsigned int)(p)[3]<<24)  )
+
+#define CHACHA_KEY_SIZE         32
+#define CHACHA_CTR_SIZE         16
+#define CHACHA_BLK_SIZE         64
+
+#endif