We Keep Coding

How to Parse received Hex bytes into readable string

As the title says, I've been working on MiFare Classic reading a card.
I'm using the MiFare v1.1.3 Library from NuGet
and it returns a byte array, which I parse to readable Hex strings, by looping thru it.
Here's the code snippet:
int sector = 1;
int block = 0;
int size = 16;
var data = await localCard.GetData(sector, block, size);
string hexString = "";
for (int i = 0; i < data.Length; i++)
{
hexString += data[i].ToString("X2") + " ";
}
// hexString returns 84 3D 17 B0 1E 08 04 00 02 63 B5 F6 B9 BE 77 1D
Now, how can I parse it properly?
I've tried parsing it into ASCII, ANSI, Int, Int64, Base64, Long
and all of them didn't match the 'data' that it's suppose to contain
EDIT:
The expected output: 1206058
HEX String returned: 84 3D 17 B0 1E 08 04 00 02 63 B5 F6 B9 BE 77 1D

I've checked the source code
it looks like both Task<byte[]> GetData Task SetData methods do not have any special logic to transform the data. Data are just saved (and read) as byte[]
I suppose that you have to contact author/company that has wrote data you are trying to read.
The expected output: 1206058
Looks strange since you are reading 16 bytes size = 16 and expecting 7 characters to be read.
Is it possible that block or sector values are incorrect ?

I have written a simple program to solve your problem. Perhaps this is what you want to achieve:
// The original byte data array; some random data
byte[] data = { 0, 1, 2, 3, 4, 85, 128, 255 };
// Byte data -> Hex string
StringBuilder hexString = new StringBuilder();
foreach (byte item in data)
{
hexString.Append($"{item.ToString("X2")} ");
}
Console.WriteLine(hexString.ToString().Trim());
// Hex string -> List of bytes
string[] hexArray = hexString.ToString().Trim().Split(' ');
List<byte> dataList = new List<byte>();
foreach (string item in hexArray)
{
dataList.Add(byte.Parse(item, System.Globalization.NumberStyles.HexNumber));
}
dataList.ForEach(b => Console.Write($"{b} "));
Console.WriteLine();
If it is not the right solution please provide us more info about your problem.

If var data potentially is string - you can reverse it from hex by:
// To Hex
byte[] plainBytes = Encoding.ASCII.GetBytes("MiFare v1.1.3");
string hexString = "";
for (int i = 0; i < plainBytes.Length; i++)
hexString += plainBytes[i].ToString("X2") + " ";
Console.WriteLine(hexString); // Result: "4D 69 46 61 72 65 20 76 31 2E 31 2E 33"
// From Hex
hexString = hexString.Replace(" ", ""); // Remove whitespaces to have "4D69466172652076312E312E33"
byte[] hexBytes = new byte[hexString.Length / 2];
for (int i = 0; i < hexString.Length / 2; i++)
hexBytes[i] = Convert.ToByte(hexString.Substring(2 * i, 2), 16);
string plainString = Encoding.ASCII.GetString(hexBytes);
Console.WriteLine(plainString); // Result: "MiFare v1.1.3"
Just, probably, should be needed to define correct Encoding.

C# Convert Active Directory Hexadecimal to GUID

We are pushing AD objects to a 3rd party vendor where the objectGUID attribute is outputted as hexadecimal, as seen in the Attribute Editor window. We need to be able to convert the hexadecimal back to GUID format so that we can perform lookups against the database.
Is it possible to convert hexadecimal back to GUID format? In all likelihood, the hexadecimal will come back in string format.
Example:
Hexadecimal: EC 14 70 17 FD FF 0D 40 BC 03 71 A8 C5 D9 E3 02
or
Hexadecimal (string): ec147017fdff0d40bc0371a8c5d9e302
GUID: 177014EC-FFFD-400D-BC03-71A8C5D9E302
Update
After accepting the answer, I can validate it using some code from Microsoft See here: Guid.ToByteArray Method
using System;
namespace ConsoleApp3
{
class Program
{
static void Main()
{
// https://stackoverflow.com/questions/56638890/c-sharp-convert-active-directory-hexadecimal-to-guid
byte[] bytearray = StringToByteArray("ec147017fdff0d40bc0371a8c5d9e302");
// https://learn.microsoft.com/en-us/dotnet/api/system.guid.tobytearray?view=netframework-4.8
Guid guid = new Guid(bytearray);
Console.WriteLine("Guid: {0}", guid);
Byte[] bytes = guid.ToByteArray();
foreach (var byt in bytes)
Console.Write("{0:X2} ", byt);
Console.WriteLine();
Guid guid2 = new Guid(bytes);
Console.WriteLine("Guid: {0} (Same as First Guid: {1})", guid2, guid2.Equals(guid));
Console.ReadLine();
}
public static byte[] StringToByteArray(String hex)
{
int NumberChars = hex.Length;
byte[] bytes = new byte[NumberChars / 2];
for (int i = 0; i < NumberChars; i += 2)
bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
return bytes;
}
}
}

Guid has a constructor which takes a byte array
You can convert the hexadecimal string into a byte array and use that to construct a new Guid.
If you need to know how to convert the hexadecimal string to a byte array, Stack Overflow already has a few answers to that question.
From the accepted answer of that question:
public static byte[] StringToByteArray(String hex)
{
int NumberChars = hex.Length;
byte[] bytes = new byte[NumberChars / 2];
for (int i = 0; i < NumberChars; i += 2)
bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
return bytes;
}

Replace Hex String in File

After banging my head on it for hours, I am at my wits end. I have a hex string in a file that is "68 39 30 00 00". The "39 30" is the decimal value "12345" which I am wanting to replace, and the "68" and "00 00" are just to ensure there is a single match.
I want to pass in a new decimal value such as "12346", and replace the existing value in the file. I have tried converting everything back and fourth between hex, byte arrays, and so on and feel it has to be much simpler than I am making it out to be.
static void Main(string[] args)
{
// Original Byte string to find and Replace "12345"
byte[] original = new byte[] { 68, 39, 30, 00, 00 };
int newPort = Convert.ToInt32("12346");
string hexValue = newPort.ToString("X2");
byte[] byteValue = StringToByteArray(hexValue);
// Build Byte Array of the port to replace with. Starts with /x68 and ends with /x00/x00
byte[] preByte = new byte[] { byte.Parse("68", System.Globalization.NumberStyles.HexNumber) };
byte[] portByte = byteValue;
byte[] endByte = new byte[] { byte.Parse("00", System.Globalization.NumberStyles.HexNumber), byte.Parse("00", System.Globalization.NumberStyles.HexNumber) };
byte[] replace = new byte[preByte.Length + portByte.Length + endByte.Length];
preByte.CopyTo(replace, 0);
portByte.CopyTo(replace, preByte.Length);
endByte.CopyTo(replace, (preByte.Length + portByte.Length));
Patch("Server.exe", "Server1.exe", original, replace);
}
static private byte[] StringToByteArray(string hex)
{
return Enumerable.Range(0, hex.Length)
.Where(x => x % 2 == 0)
.Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
.ToArray();
}

The decimal value of 39 30 is 14640 so it will check for the 14640 which is not present.
Hex value for 12345 is 30 39. Just correct the values and your program will work fine.

Verify DSA Signature generated by Java in C#

I know this is a topic with lots of existing questions but I am failing to find any existing answers which cover my exact case.
I need to sign a string (a URL) in some Java code and deliver the string along with the signature to a C# program.
I run the following Java code once to generate a DSA keypair:
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA", "SUN");
SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN");
keyGen.initialize(1024, random);
KeyPair pair = keyGen.generateKeyPair();
PrivateKey priv = pair.getPrivate();
PublicKey pub = pair.getPublic();
/* save the private key in a file */
byte[] privkey = priv.getEncoded();
FileOutputStream privkeyfos = new FileOutputStream("key.priv");
privkeyfos.write(privkey);
privkeyfos.close();
/* save the public key in a file */
byte[] pubkey = pub.getEncoded();
FileOutputStream pubkeyfos = new FileOutputStream("key.public");
pubkeyfos.write(pubkey);
pubkeyfos.close();
I am then using the following code to generate the signature.
public static String Sign(String keyPath, byte[] data)
{
FileInputStream keyfis = new FileInputStream(new File(keyPath, "key.priv"));
byte[] encKey = new byte[keyfis.available()];
keyfis.read(encKey);
keyfis.close();
PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(encKey);
KeyFactory keyFactory = KeyFactory.getInstance("DSA");
PrivateKey privKey = keyFactory.generatePrivate(privKeySpec);
Signature dsa = Signature.getInstance("SHA1withDSA", "SUN");
dsa.initSign(privKey);
ByteArrayInputStream in = new ByteArrayInputStream(data);
BufferedInputStream bufin = new BufferedInputStream(in);
byte[] buffer = new byte[1024];
int len;
while ((len = bufin.read(buffer)) >= 0)
{
dsa.update(buffer, 0, len);
}
bufin.close();
byte[] realSig = dsa.sign();
return new String(Base64.encodeBase64(realSig), "UTF-8");
}
In my C# code I have access to the string, the Base64 encoded signature and the "key.public" file from the first step.
Can anyone provide a block of code which combines these elements along with a suitable library to determine whether the string has been tampered with?

I have now solved this with some key input coming from this article: http://www.codeproject.com/KB/security/CryptoInteropSign.aspx
The main verification is done using the following C# function.
private static Boolean isValid(String xiString, String xiSig)
{
AsnKeyParser keyParser = new AsnKeyParser("path/to/key.public");
DSAParameters publicKey = keyParser.ParseDSAPublicKey();
DSACryptoServiceProvider DSA = new DSACryptoServiceProvider();
DSA.ImportParameters(publicKey);
DSASignatureDeformatter DSADeformatter = new DSASignatureDeformatter(DSA);
UTF8Encoding UTF8 = new UTF8Encoding();
byte[] plainBytes = UTF8.GetBytes(xiString);
var sha1 = new SHA1Managed();
var hash = sha1.ComputeHash(plainBytes);
byte[] asn1SigBytes = Convert.FromBase64String(xiSig);
byte[] sigBytes = ConvertToP1363Signature(asn1SigBytes);
Boolean retVal = DSADeformatter.VerifySignature(hash, sigBytes);
return retVal;
}
This relies on two helper methods.
1) AsnKeyParser is a class attached to the linked article. The article offers a C# download from which I used two files: AsnKeyParser.cs and BerDecodeError.cs. I deleted the RSA functions from AsnKeyParser to remove the dependency on the BigInteger file.
This class handles parsing the "key.public" file created by my Java code.
2) A function for converting the 46-48 byte DER encoded signature generated by Java into a DSA signature which C# will accept.
This function is based on code in the comments of the linked article.
private static byte[] ConvertToP1363Signature(byte[] ASN1Sig)
{
AsnParser asn = new AsnParser(ASN1Sig);
asn.NextSequence();
byte[] r = asn.NextInteger();
byte[] s = asn.NextInteger();
// Returned to caller
byte[] p1363Signature = new byte[40];
if (r.Length > 21 || (r.Length == 21 && r[0] != 0))
{
// WTF???
// Reject - signature verification failed
}
else if (r.Length == 21)
{
// r[0] = 0
// r[1]'s high bit *should* be set
Array.Copy(r, 1, p1363Signature, 0, 20);
}
else if (r.Length == 20)
{
// r[0]'s high bit *should not* be set
Array.Copy(r, 0, p1363Signature, 0, 20);
}
else
{
// fewer than 20 bytes
int len = r.Length;
int off = 20 - len;
Array.Copy(r, 0, p1363Signature, off, len);
}
if (s.Length > 21 || (s.Length == 21 && s[0] != 0))
{
// WTF???
// Reject - signature verification failed
}
else if (s.Length == 21)
{
// s[0] = 0
// s[1]'s high bit *should* be set
Array.Copy(s, 1, p1363Signature, 20, 20);
}
else if (s.Length == 20)
{
// s[0]'s high bit *should not* be set
Array.Copy(s, 0, p1363Signature, 20, 20);
}
else
{
// fewer than 20 bytes
int len = s.Length;
int off = 40 - len;
Array.Copy(s, 0, p1363Signature, off, len);
}
return p1363Signature;
}

How to convert a String to a Hex Byte Array? [duplicate]

This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
How do you convert Byte Array to Hexadecimal String, and vice versa, in C#?
For testing my encryption algorithm I have being provided keys, plain text and their resulting cipher text.
The keys and plaintext are in strings
How do i convert it to a hex byte array??
Something like this : E8E9EAEBEDEEEFF0F2F3F4F5F7F8F9FA
To something like this :
byte[] key = new byte[16] { 0xE8, 0xE9, 0xEA, 0xEB, 0xED, 0xEE, 0xEF, 0xF0, 0xF2, 0xF3, 0xF4, 0xF5, 0xF7, 0xF8, 0xF9, 0xFA} ;
Thanx in advance :)

Do you need this?
static class HexStringConverter
{
public static byte[] ToByteArray(String HexString)
{
int NumberChars = HexString.Length;
byte[] bytes = new byte[NumberChars / 2];
for (int i = 0; i < NumberChars; i += 2)
{
bytes[i / 2] = Convert.ToByte(HexString.Substring(i, 2), 16);
}
return bytes;
}
}
Hope it helps.

Sample code from MSDN:
string hexValues = "48 65 6C 6C 6F 20 57 6F 72 6C 64 21";
string[] hexValuesSplit = hexValues.Split(' ');
foreach (String hex in hexValuesSplit)
{
// Convert the number expressed in base-16 to an integer.
int value = Convert.ToInt32(hex, 16);
// Get the character corresponding to the integral value.
string stringValue = Char.ConvertFromUtf32(value);
char charValue = (char)value;
Console.WriteLine("hexadecimal value = {0}, int value = {1}, char value = {2} or {3}", hex, value, stringValue, charValue);
}
You only have to change it to split the string on every 2 chars instead of on spaces.

did u mean this
StringBuilder Result = new StringBuilder();
string HexAlphabet = "0123456789ABCDEF";
foreach (byte B in Bytes)
{
Result.Append(HexAlphabet[(int)(B >> 4)]);
Result.Append(HexAlphabet[(int)(B & 0xF)]);
}
return Result.ToString();