MD5 Hashing between VB.net and PHP

Question

Answered with the help of @JonSkeet

Given this code:

    Dim data1ToHash As Byte() = (New UnicodeEncoding).GetBytes(input)
    ' 2. Hash the byte array
    Dim hashvalue1 As Byte() = CType(CryptoConfig.CreateFromName("MD5"), HashAlgorithm).ComputeHash(data1ToHash)

Shouldn't this PHP produce the correct hash?

$md5 = (md5(utf8_encode($signature), true));

I tried, but the md5sums aren't matching up. I assumed it was encoding, but perhaps it has to do with the byte array, can anyone shed some light on this? FYI I can't change the VB

To compare the results:

in .Net

For Each b As Byte In hashvalue1
  tb.Text = tb.Text & b.ToString() & ","
Next
tb.Text = tb.Text.Trim(",")

in PHP

print_r(unpack('C*', pack('H*', md5($signature))))

as per another question

possible duplicate of How to mimic computeHash vb function in PHP — DaveRandom
– DaveRandom, Commented Dec 15, 2011 at 15:05

Community · Accepted Answer · 2023-11-17 20:42:18Z

4

It's not clear how you're comparing the results, but the encoding is *definitely a problem - you're using UTF-16 in the VB code, and UTF-8 in the PHP. You can change the VB code like this:

Dim data1ToHash As Byte() = Encoding.UTF8.GetBytes(input)

The MD5 part can also be simplified, giving this result:

Dim unhashed As Byte() = Encoding.UTF8.GetBytes(input)
Dim hashed As Byte() = MD5.Create().ComputeHash(unhashed)

EDIT: If you can't change the VB, you need to change the PHP to use UTF-16, potentially with mbstring as suggested in comments. You'll need to know what the existing encoding is, of course...

edited Nov 17, 2023 at 20:42

CommunityBot

11 silver badge

answered Dec 15, 2011 at 15:06

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

scottkf Over a year ago

Good point, I'll update the post, but I'm afraid I can't change the VB.

vcsjones Over a year ago

@scottkf You could probably use mbstring from your PHP to convert from UTF8 to UTF16.

scottkf Over a year ago

@jon-skeet then shouldn't the following produce correct results? $string = mb_convert_encoding(utf8_encode($signature), 'UTF-8', 'UTF-16'); $md5 = (md5($string, true));

Jon Skeet Over a year ago

@scottkf: No, because you're then still encoding the UTF-16 version as UTF-8 (in a way which is broken, actually, as the input to utf8_encode expects iso-8859-1) before passing it to md5. Without the final utf8_encode that might be okay. But I don't know enough about PHP's string representation to know for sure.

scottkf Over a year ago

@JonSkeet: The problem was in the representation of the bytes. VB.net was using LE for UTF-16, whereas PHP's UTF-16 is actually big endian. The solution is: $string = mb_convert_encoding($signature, 'UTF-16LE', 'UTF-8'); $encoded_signature = base64_encode(md5($string, true)); It was verified by doing: $raw = unpack('C*', $string); print_r($raw);

|

scottkf · Accepted Answer · 2011-12-16 02:52:39Z

0

The solution had to do with byte ordering: .NET in UTF-16 was Little Endian, whereas PHP's default UTF-16 encoding is Big Endian. So the answer is:

mb_internal_encoding('UTF-8');
$string = mb_convert_encoding($signature, 'UTF-16LE', 'UTF-8');
$encoded_signature = base64_encode(md5($string, true));

To verify, I compared the UTF-16 encoded bytes in PHP and .NET:

print_r(unpack('C*', $string));

Just that simple. Thanks to everyone who helped, especially @JonSkeet.

answered Dec 16, 2011 at 2:52

scottkf

1853 silver badges9 bronze badges

Collectives™ on Stack Overflow

MD5 Hashing between VB.net and PHP

2 Answers 2

6 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related