challenge: do challenge 28

1 files changed, 59 insertions, 0 deletions

diff --git a/challenge/c28.go b/challenge/c28.go
new file mode 100644
index 0000000..7a763d5
--- /dev/null
+++ b/challenge/c28.go
@@ -0,0 +1,59 @@
+// Copyright © 2021 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package challenge
+
+import (
+	"fmt"
+
+	"ricketyspace.net/cryptopals/lib"
+)
+
+func C28() {
+	msg := lib.StrToBytes(`Nobody knows, why we keep tryin'
+Why we keep tryin'
+
+And so on it goes, I'm looking forward
+To the next letter that I'm gonna get from you
+
+A baby is born, as a man lay dying
+As a man lay dying
+
+And so on it goes, I'm looking forward
+To the next letter that I'm gonna get from you
+
+Sit beside me, watch the world burn
+We'll never learn, we don't deserve nice things
+
+And we'll scream, self-righteously
+We did our best but what does that really mean
+
+I'm walkin' around, walkin' around
+With my head down, my head down
+
+I'm pushin' away, I'm pushin' away
+Yeah I'm pushin' away, pushin' away`)
+	sec := lib.StrToBytes("Milk Records")
+
+	// Generate SHA1 MAC.
+	mac := lib.Sha1Mac(sec, msg)
+
+	// Verify.
+	if lib.Sha1MacVerify(sec, msg, mac) != true {
+		fmt.Printf("Error: Sha1Mac verification failed!\n")
+		return
+	}
+
+	// Modify msg
+	msg[42] = byte(42)
+
+	// Verify that SHA1 MAC fails
+	if lib.Sha1MacVerify(sec, msg, mac) != false {
+		fmt.Printf("Error: Sha1Mac verification success!\n")
+		return
+	}
+	fmt.Printf("OK\n")
+}
+
+// Output:
+// OK