X-Git-Url: http://git.euphorik.ch/?a=blobdiff_plain;f=labo2-fsharp%2FCryptoFileTests%2FTests.fs;h=eb8a2902805fe33956e32b1309f771c1a70028ec;hb=0508ca9ddb817b14ca747f8736ea1960cb70d2e7;hp=dd1b3e04ba9b5848d324f7784a8887cfce505adf;hpb=61a8b3492e89e883b23c158eb52ba2b070234df8;p=crypto_lab2.git

diff --git a/labo2-fsharp/CryptoFileTests/Tests.fs b/labo2-fsharp/CryptoFileTests/Tests.fs
index dd1b3e0..eb8a290 100644
--- a/labo2-fsharp/CryptoFileTests/Tests.fs
+++ b/labo2-fsharp/CryptoFileTests/Tests.fs
@@ -24,10 +24,12 @@ let doSomeTests () =
     let decrypt () = 
         API.decryptFile cipherFilename "." keySigPub keyCryptPriv
 
-    let writeByteToCipherFileAt byte position = 
-        using (new FileStream (cipherFilename, FileMode.Open, FileAccess.Write))
+    let incrementByteCipherFileAt position = 
+        using (new FileStream (cipherFilename, FileMode.Open, FileAccess.ReadWrite))
               (fun fs -> fs.Position <- position
-                         fs.Write ([| byte |], 0, 1))
+                         let byte = fs.ReadByte () |> byte
+                         fs.Position <- position
+                         fs.Write ([| byte + 1uy |], 0, 1)) // Automatically modulo 256.
 
     encrypt ()
     File.Delete plainFilename
@@ -35,7 +37,7 @@ let doSomeTests () =
     assert (File.ReadAllText plainFilename = fileContent)
 
     printfn "== Altering the MAC..."
-    writeByteToCipherFileAt 0uy 0L
+    incrementByteCipherFileAt 0L
     try
         decrypt ()
         assert false
@@ -44,7 +46,7 @@ let doSomeTests () =
 
     printfn "== Altering the signature..."
     encrypt ()
-    writeByteToCipherFileAt 0uy 32L
+    incrementByteCipherFileAt 32L
     try
         decrypt ()
         assert false
@@ -53,16 +55,16 @@ let doSomeTests () =
 
     printfn "== Altering the keys..."
     encrypt ()
-    writeByteToCipherFileAt 0uy (32L + 256L)
+    incrementByteCipherFileAt (32L + 256L)
     try
         decrypt ()
         assert false
     with
         | error -> assert (error :? UnableToDecryptAESKeys)
 
-    printfn "== Altering the cyphering..."
+    printfn "== Altering the cyphertext..."
     encrypt ()
-    writeByteToCipherFileAt 0uy (32L + 256L + 256L)
+    incrementByteCipherFileAt (32L + 256L + 256L)
     try
         decrypt ()
         assert false