From 79ff7517a45a37ad542d3c24cfc5653b747b7e77 Mon Sep 17 00:00:00 2001
From: Christian Hermann <c.hermann@bitbeans.de>
Date: Mon, 4 May 2015 17:24:51 +0200
Subject: [PATCH] BSC-01-008

- Checksum prefix is now INSIDE the checksum and useful ...
---
 StreamCryptor/Model/EncryptedFileChunk.cs  | 14 ++++++--------
 StreamCryptor/Model/EncryptedFileFooter.cs | 12 ++++++------
 StreamCryptor/Model/EncryptedFileHeader.cs | 21 ++++++++++-----------
 3 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/StreamCryptor/Model/EncryptedFileChunk.cs b/StreamCryptor/Model/EncryptedFileChunk.cs
index cee3857..c872428 100644
--- a/StreamCryptor/Model/EncryptedFileChunk.cs
+++ b/StreamCryptor/Model/EncryptedFileChunk.cs
@@ -44,10 +44,9 @@ public class EncryptedFileChunk
         /// <param name="chunkChecksumLength">The length of the checksum.</param>
         public void SetChunkChecksum(byte[] ephemeralKey, int chunkChecksumLength)
         {
-            ChunkChecksum = ArrayHelpers.ConcatArrays(_checksumChunkPrefix,
-                GenericHash.Hash(ArrayHelpers.ConcatArrays(Chunk,
-                    Utils.IntegerToLittleEndian(ChunkLength)),
-                    Utils.GetEphemeralHashKey(ephemeralKey), chunkChecksumLength));
+            ChunkChecksum = GenericHash.Hash(ArrayHelpers.ConcatArrays(_checksumChunkPrefix, Chunk,
+                Utils.IntegerToLittleEndian(ChunkLength)),
+                Utils.GetEphemeralHashKey(ephemeralKey), chunkChecksumLength);
         }
 
         /// <summary>
@@ -58,10 +57,9 @@ public void SetChunkChecksum(byte[] ephemeralKey, int chunkChecksumLength)
         /// <exception cref="BadFileChunkException"></exception>
         public void ValidateChunkChecksum(byte[] ephemeralKey, int chunkChecksumLength)
         {
-            var chunkChecksum = ArrayHelpers.ConcatArrays(_checksumChunkPrefix,
-                GenericHash.Hash(
-                    ArrayHelpers.ConcatArrays(Chunk, Utils.IntegerToLittleEndian(ChunkLength)),
-                    Utils.GetEphemeralHashKey(ephemeralKey), chunkChecksumLength));
+            var chunkChecksum = GenericHash.Hash(
+                ArrayHelpers.ConcatArrays(_checksumChunkPrefix, Chunk, Utils.IntegerToLittleEndian(ChunkLength)),
+                Utils.GetEphemeralHashKey(ephemeralKey), chunkChecksumLength);
             if (!chunkChecksum.SequenceEqual(ChunkChecksum))
             {
                 throw new BadFileChunkException("Wrong checksum, file could be damaged or manipulated!");
diff --git a/StreamCryptor/Model/EncryptedFileFooter.cs b/StreamCryptor/Model/EncryptedFileFooter.cs
index e29d5ba..10b885e 100644
--- a/StreamCryptor/Model/EncryptedFileFooter.cs
+++ b/StreamCryptor/Model/EncryptedFileFooter.cs
@@ -30,9 +30,9 @@ public void SetFooterChecksum(byte[] chunkCount, byte[] chunkOverallLength, byte
             int footerChecksumLength)
         {
             //generate and set the Footerchecksum
-            FooterChecksum = ArrayHelpers.ConcatArrays(_checksumFooterPrefix,
-                GenericHash.Hash(ArrayHelpers.ConcatArrays(chunkCount, chunkOverallLength),
-                    Utils.GetEphemeralHashKey(ephemeralKey), footerChecksumLength));
+            FooterChecksum = GenericHash.Hash(ArrayHelpers.ConcatArrays(_checksumFooterPrefix,
+                chunkCount, chunkOverallLength),
+                Utils.GetEphemeralHashKey(ephemeralKey), footerChecksumLength);
         }
 
         /// <summary>
@@ -46,10 +46,10 @@ public void SetFooterChecksum(byte[] chunkCount, byte[] chunkOverallLength, byte
         public void ValidateFooterChecksum(byte[] chunkCount, byte[] chunkOverallLength, byte[] ephemeralKey,
             int footerChecksumLength)
         {
-            var footerChecksum = ArrayHelpers.ConcatArrays(_checksumFooterPrefix, GenericHash.Hash(
-                ArrayHelpers.ConcatArrays(chunkCount, chunkOverallLength),
+            var footerChecksum = GenericHash.Hash(
+                ArrayHelpers.ConcatArrays(_checksumFooterPrefix, chunkCount, chunkOverallLength),
                 Utils.GetEphemeralHashKey(ephemeralKey),
-                footerChecksumLength));
+                footerChecksumLength);
             //check the file footer
             if (!footerChecksum.SequenceEqual(FooterChecksum))
             {
diff --git a/StreamCryptor/Model/EncryptedFileHeader.cs b/StreamCryptor/Model/EncryptedFileHeader.cs
index 57fef0c..e17fbe7 100644
--- a/StreamCryptor/Model/EncryptedFileHeader.cs
+++ b/StreamCryptor/Model/EncryptedFileHeader.cs
@@ -133,14 +133,13 @@ public void ProtectFileName(string fileName, int fileNameLength)
         /// <param name="headerChecksumLength">The length of the checksum.</param>
         public void SetHeaderChecksum(int headerChecksumLength)
         {
-            HeaderChecksum = ArrayHelpers.ConcatArrays(_checksumHeaderPrefix,
-                GenericHash.Hash(ArrayHelpers.ConcatArrays(BaseNonce,
-                    FilenameNonce, Filename,
-                    Utils.IntegerToLittleEndian(Version),
-                    Key,
-                    BitConverter.GetBytes(UnencryptedFileLength)),
-                    Utils.GetEphemeralHashKey(UnencryptedEphemeralKey),
-                    headerChecksumLength));
+            HeaderChecksum = GenericHash.Hash(ArrayHelpers.ConcatArrays(_checksumHeaderPrefix, BaseNonce,
+                FilenameNonce, Filename,
+                Utils.IntegerToLittleEndian(Version),
+                Key,
+                BitConverter.GetBytes(UnencryptedFileLength)),
+                Utils.GetEphemeralHashKey(UnencryptedEphemeralKey),
+                headerChecksumLength);
         }
 
         /// <summary>
@@ -151,14 +150,14 @@ public void SetHeaderChecksum(int headerChecksumLength)
         /// <exception cref="BadFileHeaderException"></exception>
         public void ValidateHeaderChecksum(byte[] ephemeralKey, int headerChecksumLength)
         {
-            var headerChecksum = ArrayHelpers.ConcatArrays(_checksumHeaderPrefix, GenericHash.Hash(
-                ArrayHelpers.ConcatArrays(BaseNonce,
+            var headerChecksum = GenericHash.Hash(
+                ArrayHelpers.ConcatArrays(_checksumHeaderPrefix, BaseNonce,
                     FilenameNonce, Filename,
                     Utils.IntegerToLittleEndian(Version),
                     Key,
                     BitConverter.GetBytes(UnencryptedFileLength)),
                 Utils.GetEphemeralHashKey(ephemeralKey),
-                headerChecksumLength));
+                headerChecksumLength);
             if (!headerChecksum.SequenceEqual(HeaderChecksum))
             {
                 throw new BadFileHeaderException("Malformed file header: file could be damaged or manipulated!");