From 46a83398b4cafa6c731816277919e84fab2206b2 Mon Sep 17 00:00:00 2001
From: Peter Rounce <peter@rounce.me.uk>
Date: Sat, 16 Sep 2023 15:26:22 +0100
Subject: [PATCH] clarify counter value

---
 .gitignore           |  1 +
 cli/main.go          | 10 +++++++---
 docs/TEST_VECTORS.md |  6 +++---
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/.gitignore b/.gitignore
index 43f5114..69b774b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@
 boltcard
 createboltcard/createboltcard
 wipeboltcard/wipeboltcard
+cli/cli
 
 # Test binary, built with `go test -c`
 *.test
diff --git a/cli/main.go b/cli/main.go
index dc397bf..dc56c20 100644
--- a/cli/main.go
+++ b/cli/main.go
@@ -25,9 +25,9 @@ func check_cmac(uid []byte, ctr []byte, k2_cmac_key []byte, cmac []byte) (bool,
 	sv2[10] = uid[4]
 	sv2[11] = uid[5]
 	sv2[12] = uid[6]
-	sv2[13] = ctr[0]
+	sv2[13] = ctr[2]
 	sv2[14] = ctr[1]
-	sv2[15] = ctr[2]
+	sv2[15] = ctr[0]
 
 	cmac_verified, err := crypto.Aes_cmac(k2_cmac_key, sv2, cmac)
 
@@ -108,7 +108,11 @@ func main() {
 	}
 
 	uid := dec_p[1:8]
-	ctr := dec_p[8:11]
+	
+  ctr := make([]byte, 3)
+	ctr[0] = dec_p[10]
+	ctr[1] = dec_p[9]
+	ctr[2] = dec_p[8]
 
 	// set up uid & ctr for card record if needed
 
diff --git a/docs/TEST_VECTORS.md b/docs/TEST_VECTORS.md
index ec81acd..68c12a8 100644
--- a/docs/TEST_VECTORS.md
+++ b/docs/TEST_VECTORS.md
@@ -10,7 +10,7 @@ c =  E19CCB1FED8892CE
 aes_decrypt_key =  0c3b25d92b38ae443229dd59ad34b85d
 aes_cmac_key =  b45775776cb224c75bcde7ca3704e933
 
-decrypted card data : uid 04996c6a926980 , ctr 030000
+decrypted card data : uid 04996c6a926980 , ctr 000003
 cmac validates ok
 
 
@@ -22,7 +22,7 @@ c =  66B4826EA4C155B4
 aes_decrypt_key =  0c3b25d92b38ae443229dd59ad34b85d
 aes_cmac_key =  b45775776cb224c75bcde7ca3704e933
 
-decrypted card data : uid 04996c6a926980 , ctr 050000
+decrypted card data : uid 04996c6a926980 , ctr 000005
 cmac validates ok
 
 
@@ -34,7 +34,7 @@ c =  CC61660C020B4D96
 aes_decrypt_key =  0c3b25d92b38ae443229dd59ad34b85d
 aes_cmac_key =  b45775776cb224c75bcde7ca3704e933
 
-decrypted card data : uid 04996c6a926980 , ctr 070000
+decrypted card data : uid 04996c6a926980 , ctr 000007
 cmac validates ok
 
 ```