Duplicate Microsoft FCIV MD5 file hash ?

[andrewcw]

I have a VB 5 module that duplicates the FCIV.exe from Microsoft. I need to
move an application forward to C#, but the samples for MD5 hash using the
framework I tried gave different hashes. What do I feed the framework and
how do I get the same values ??

The following code DOES NOT GIVE THE FCIV value:

public string getFileHash(str ing filePath)
{
string retVal = "";
// open file
try
{
FileInfo fi = new FileInfo(filePa th);
long fileLength = fi.Length;
string fileString = Convert.ToStrin g(fileLength);
retVal = Md5Hash(fileStr ing); // method 1
string retVal2 = Md5Hash2(fileSt ring); // method 2
retVal = retVal + " : " + retVal2;
}
catch (Exception e)
{
Console.WriteLi ne(e.Message);
retVal = "";
}
return retVal;

}

public static string Md5Hash(string pass)
{
MD5 md5 = MD5CryptoServic eProvider.Creat e();
byte[] dataMd5 = md5.ComputeHash (Encoding.Defau lt.GetBytes(pas s));
StringBuilder sb = new StringBuilder() ;
for (int i = 0; i < dataMd5.Length; i++)
sb.AppendFormat ("{0:x2}", dataMd5[i]);
return sb.ToString();

}
public static string Md5Hash2(string str)
{

// Create a buffer large enough to hold the string
byte[] unicodeText = new byte[str.Length * 2];
Encoder enc = System.Text.Enc oding.Unicode.G etEncoder();
// Now that we have a byte array we can ask the CSP to hash it
MD5 md5 = new MD5CryptoServic eProvider();
byte[] result = md5.ComputeHash (unicodeText);

// Build the final string by converting each byte
// into hex and appending it to a StringBuilder
StringBuilder sb = new StringBuilder() ;
for (int i = 0; i < result.Length; i++)
{
sb.Append(resul t[i].ToString("X2") );
}

// And return it
return sb.ToString();

}


--
Andrew

[Jon Skeet [C# MVP]]

andrewcw <an******@acw.c om> wrote:

I have a VB 5 module that duplicates the FCIV.exe from Microsoft. I need to
move an application forward to C#, but the samples for MD5 hash using the
framework I tried gave different hashes. What do I feed the framework and
how do I get the same values ??

You're producing two hashes from the same string, but you're encoding
the string in a different way. (In fact, in one case you're not
encoding it at all - you're just getting the hash of an array of 0s.)
Why would you expect that to give the same result?

It's not at all clear why you're trying to get a hashcode of a
representation of the length of the file though - for one thing, that's
bound to be precisely representable in less data than the hash itself.

Are you aware that neither of your hash mechanisms is actually looking
at the *contents& of the file?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[andrewcw]

Jon,

Thanks for pointing out my misunderstandin g. Does anyone know how the hash
would be created as MS does in FCIV ? The VB code does but exactly what it
is doing and how that maps to the .NET frameworks - I dont know. Any idea ??
--
Andrew
"Jon Skeet [C# MVP]" wrote:

andrewcw <an******@acw.c om> wrote:

I have a VB 5 module that duplicates the FCIV.exe from Microsoft. I need to
move an application forward to C#, but the samples for MD5 hash using the
framework I tried gave different hashes. What do I feed the framework and
how do I get the same values ??

You're producing two hashes from the same string, but you're encoding
the string in a different way. (In fact, in one case you're not
encoding it at all - you're just getting the hash of an array of 0s.)
Why would you expect that to give the same result?

It's not at all clear why you're trying to get a hashcode of a
representation of the length of the file though - for one thing, that's
bound to be precisely representable in less data than the hash itself.

Are you aware that neither of your hash mechanisms is actually looking
at the *contents& of the file?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[andrewcw]

Jon,

Here's how I re-wrote the code based on my limited understanding - but it
still is different - ideas ?? It seems odd to me that the encoding wants a
char array, so I go through some contortions to the file read as a char
array. I am also uneasy that when I read, I am coercing the value to be an
integer ( the file length ).

public string getFileHash(str ing filePath)
{
string retVal = "";
try
{
FileInfo fi = new FileInfo(filePa th);
long fileLength = fi.Length;
char[] chars = new char[fileLength * 2];
TextReader streamReader = new StreamReader(fi lePath);
streamReader.Re ad(chars, 0, (int)fileLength );
MD5 md5 = MD5CryptoServic eProvider.Creat e();
//Encoding.Defaul t.GetBytes(char s);
byte[] dataMd5 =
md5.ComputeHash (Encoding.Defau lt.GetBytes(cha rs));
StringBuilder sb = new StringBuilder() ;
for (int i = 0; i < dataMd5.Length; i++)
sb.AppendFormat ("{0:x2}", dataMd5[i]);
return sb.ToString();
retVal = Md5Hash(filePat h);
}
--
Andrew
"Jon Skeet [C# MVP]" wrote:

andrewcw <an******@acw.c om> wrote:

I have a VB 5 module that duplicates the FCIV.exe from Microsoft. I need to
move an application forward to C#, but the samples for MD5 hash using the
framework I tried gave different hashes. What do I feed the framework and
how do I get the same values ??

You're producing two hashes from the same string, but you're encoding
the string in a different way. (In fact, in one case you're not
encoding it at all - you're just getting the hash of an array of 0s.)
Why would you expect that to give the same result?

It's not at all clear why you're trying to get a hashcode of a
representation of the length of the file though - for one thing, that's
bound to be precisely representable in less data than the hash itself.

Are you aware that neither of your hash mechanisms is actually looking
at the *contents& of the file?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[andrewcw]

I guess that was a good enough shove to get me thinking - here's the code
that duplicate the FCIV program for binary file ( too ).

public string getFileHashBina ry(string filePath)
{
string retVal = "";
try
{ // this works for binary files
FileInfo fi = new FileInfo(filePa th);
long fileLength = fi.Length;
MD5 md5 = MD5CryptoServic eProvider.Creat e();
FileStream fs = new FileStream(file Path, FileMode.Open);
Byte[] bBuffer = new byte[fileLength];
int something= fs.Read(bBuffer , 0,(int)fileLeng th);
byte[] dataMd5 = md5.ComputeHash (bBuffer);
fs.Close();
StringBuilder sb = new StringBuilder() ;
for (int i = 0; i < dataMd5.Length; i++)
sb.AppendFormat ("{0:x2}", dataMd5[i]);
retVal= sb.ToString();

}
catch (Exception e)
{
Console.WriteLi ne(e.Message);
retVal = "";
}
return retVal;

}

--
Andrew
"andrewcw" wrote:

Jon,

Here's how I re-wrote the code based on my limited understanding - but it
still is different - ideas ?? It seems odd to me that the encoding wants a
char array, so I go through some contortions to the file read as a char
array. I am also uneasy that when I read, I am coercing the value to be an
integer ( the file length ).

public string getFileHash(str ing filePath)
{
string retVal = "";
try
{
FileInfo fi = new FileInfo(filePa th);
long fileLength = fi.Length;
char[] chars = new char[fileLength * 2];
TextReader streamReader = new StreamReader(fi lePath);
streamReader.Re ad(chars, 0, (int)fileLength );
MD5 md5 = MD5CryptoServic eProvider.Creat e();
//Encoding.Defaul t.GetBytes(char s);
byte[] dataMd5 =
md5.ComputeHash (Encoding.Defau lt.GetBytes(cha rs));
StringBuilder sb = new StringBuilder() ;
for (int i = 0; i < dataMd5.Length; i++)
sb.AppendFormat ("{0:x2}", dataMd5[i]);
return sb.ToString();
retVal = Md5Hash(filePat h);
}
--
Andrew
"Jon Skeet [C# MVP]" wrote:

andrewcw <an******@acw.c om> wrote:

I have a VB 5 module that duplicates the FCIV.exe from Microsoft. I need to
move an application forward to C#, but the samples for MD5 hash using the
framework I tried gave different hashes. What do I feed the framework and
how do I get the same values ??

You're producing two hashes from the same string, but you're encoding
the string in a different way. (In fact, in one case you're not
encoding it at all - you're just getting the hash of an array of 0s.)
Why would you expect that to give the same result?

It's not at all clear why you're trying to get a hashcode of a
representation of the length of the file though - for one thing, that's
bound to be precisely representable in less data than the hash itself.

Are you aware that neither of your hash mechanisms is actually looking
at the *contents& of the file?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

andrewcw <an******@acw.c om> wrote:

I guess that was a good enough shove to get me thinking - here's the code
that duplicate the FCIV program for binary file ( too ).

public string getFileHashBina ry(string filePath)
{
string retVal = "";
try
{ // this works for binary files
FileInfo fi = new FileInfo(filePa th);
long fileLength = fi.Length;
MD5 md5 = MD5CryptoServic eProvider.Creat e();
FileStream fs = new FileStream(file Path, FileMode.Open);

Once you've done that, just use md5.ComputeHash (fs);
There's no need for you to read all the data in yourself.

Note that you should use a "using" statement for your stream to make
sure it gets closed even if there's an exception.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too