A trading partner has asked me to send an HMAC SHA1 hash as lowercase heaxits. The only reference I can find to them is in relation to PHP. I can do the hashing in .NET and Java but how do I output "lowercase hexits" with them? Lowercase hexits doesn't appear to be equivalent to Base64.
For lowercase hex digits (hexits) use:
public static String toHex(byte[] bytes) {
BigInteger bi = new BigInteger(1, bytes);
return String.format("%0" + (bytes.length << 1) + "x", bi);
}
From related question: In Java, how do I convert a byte array to a string of hex digits while keeping leading zeros?
Ah! I love simplicity. Here's the solution.
Public Shared Function Encrypt(ByVal plainText As String, ByVal preSharedKey As String) As String
Dim preSharedKeyBytes() As Byte = Encoding.UTF8.GetBytes(preSharedKey)
Dim plainTextBytes As Byte() = Encoding.UTF8.GetBytes(plainText)
Dim hmac = New HMACSHA1(preSharedKeyBytes)
Dim cipherTextBytes As Byte() = hmac.ComputeHash(plainTextBytes)
Dim strTemp As New StringBuilder(cipherTextBytes.Length * 2)
For Each b As Byte In cipherTextBytes
strTemp.Append(Conversion.Hex(b).PadLeft(2, "0"c).ToLower)
Next
Dim cipherText As String = strTemp.ToString
Return cipherText
End Function
This is compatible with the PHP hash_hmac function with FALSE in the raw_output parameter.
Here's a C# translation of sedge's solution:
private static String toHex(byte[] cipherTextBytes)
{
var strTemp = new StringBuilder(cipherTextBytes.Length * 2);
foreach(Byte b in cipherTextBytes)
{
strTemp.Append(Microsoft.VisualBasic.Conversion.Hex(b).PadLeft(2, '0').ToLower());
}
String cipherText = strTemp.ToString();
return cipherText;
}