Squashed 'lib/crypto-algorithms/' content from commit 100f4ff

git-subtree-dir: lib/crypto-algorithms
git-subtree-split: 100f4ff91b5a5b31a84b3999365c3058df6251ea

1 files changed, 45 insertions, 0 deletions

diff --git a/arcfour.c b/arcfour.c
new file mode 100644
index 0000000..aa7544a
--- /dev/null
+++ b/arcfour.c
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+/*********************************************************************
+* Filename:   arcfour.c
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Implementation of the ARCFOUR encryption algorithm.
+              Algorithm specification can be found here:
+               * http://en.wikipedia.org/wiki/RC4
+*********************************************************************/
+
+/*************************** HEADER FILES ***************************/
+#include <stdlib.h>
+#include "arcfour.h"
+
+/*********************** FUNCTION DEFINITIONS ***********************/
+void arcfour_key_setup(BYTE state[], const BYTE key[], int len)
+{
+	int i, j;
+	BYTE t;
+
+	for (i = 0; i < 256; ++i)
+		state[i] = i;
+	for (i = 0, j = 0; i < 256; ++i) {
+		j = (j + state[i] + key[i % len]) % 256;
+		t = state[i];
+		state[i] = state[j];
+		state[j] = t;
+	}
+}
+
+void arcfour_generate_stream(BYTE state[], BYTE out[], size_t len)
+{
+	int i, j;
+	size_t idx;
+	BYTE t;
+
+	for (idx = 0, i = 0, j = 0; idx < len; ++idx)  {
+		i = (i + 1) % 256;
+		j = (j + state[i]) % 256;
+		t = state[i];
+		state[i] = state[j];
+		state[j] = t;
+		out[idx] = state[(state[i] + state[j]) % 256];
+	}
+}