From 3b0fb163cbac08a36b01f186b72e2a9cee4b7a2d Mon Sep 17 00:00:00 2001
From: rsiddharth <s@ricketyspace.net>
Date: Sat, 29 Aug 2020 20:00:53 -0400
Subject: challenge: do challenge 3

* challenge/c03.go: Implement challenge 3
* cryptopals.go (main): Add handling to run challenge 3
* lib/brute.go (XORCrackSingleKey): New function.
* lib/hex.go (HexStrToAsciiStr, ByteToHexStr): New functions.
* lib/str.go (FillStr): New function.
---
 lib/hex.go | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

(limited to 'lib/hex.go')

diff --git a/lib/hex.go b/lib/hex.go
index bf539bc..6fe7e6a 100644
--- a/lib/hex.go
+++ b/lib/hex.go
@@ -24,3 +24,32 @@ func DecToHexChar(i uint16) byte {
 	}
 	return 0
 }
+
+// 'h' must be hex encoded string.
+func HexStrToAsciiStr(h string) string {
+	a := ""
+	lh := len(h)
+
+	if lh < 1 {
+		return a
+	}
+	if lh == 1 {
+		return string(HexCharToDec(h[0]))
+	}
+
+	for i := 0; i < lh; i += 2 {
+		b := HexCharToDec(h[i])<<4 | HexCharToDec(h[i+1])
+		a += string(b)
+	}
+	return a
+}
+
+func ByteToHexStr(b byte) string {
+	p := DecToHexChar(uint16(b >> 4))
+	q := DecToHexChar(uint16(b & 0xf))
+
+	s := string(p)
+	s += string(q)
+
+	return s
+}
-- 
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