do challenge 13

2 files changed, 32 insertions, 0 deletions

diff --git a/challenge/ch13.go b/challenge/ch13.go
new file mode 100644
index 0000000..357a802
--- /dev/null
+++ b/challenge/ch13.go
@@ -0,0 +1,30 @@
+// Copyright © 2020 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package challenge
+
+import (
+	"fmt"
+	"ricketyspace.net/cryptopals/lib"
+)
+
+func C13() {
+	adminBlock := lib.BytesToStr(lib.Pkcs7Padding(lib.StrToBytes("admin"), 16))
+	ep := lib.WebProfileFor("foo@abacus" + adminBlock)
+	encryptedEP := lib.WebEncryptProfile(ep)
+	adminBlockCipher := encryptedEP[16:32] // Second block in the cipher
+
+	ep = lib.WebProfileFor("foo@abacus")
+	encryptedEP = lib.WebEncryptProfile(ep)
+	for i := 0; i < 16; i++ { // Replace last block with the admin cipher block.
+		encryptedEP[32+i] = adminBlockCipher[i]
+	}
+	adminEP := lib.WebDecryptProfile(encryptedEP)
+	adminProfile := lib.WebDecodeProfile(adminEP)
+	fmt.Printf("Admin Encoded Profile: %v\n", adminEP)
+	fmt.Printf("Admin Profile: %v\n", adminProfile)
+}
+
+// Output:
+// Admin Encoded Profile: email=foo@abacus&uid=10001&role=admin
+// Admin Profile: map[email:foo@abacus role:admin uid:10001]
diff --git a/cryptopals.go b/cryptopals.go
index 3100115..1ae8c8d 100644
--- a/cryptopals.go
+++ b/cryptopals.go
@@ -42,5 +42,7 @@ func main() {
 		challenge.C11()
 	case 12:
 		challenge.C12()
+	case 13:
+		challenge.C13()
 	}
 }