Hex to string

[Guest]

Hi,

Have a symmetric encryption method that returns a base64 string. I then get
the hex representation of that string with the code below

public static string Base64ToHex(string input)
{
StringBuilder sb = new StringBuilder();
byte[] inputBytes = Encoding.UTF8.GetBytes(input);

foreach(byte b in inputBytes)
{
sb.Append(string.Format("{0:x2}", b));
}

return sb.ToString();
}

My question is: How do I get the hex string back to base64 string?

Ex.
base64: NuZ5uF0MHtJ54nMc+79t/NR9GAmmaY3vUJu7fZyvww0=
hexfrombase64: 4e755a357546304d48744a35346e4d632b3739742f4e523947416d6d6159
3376554a7537665a79767777303d
base64fromhex: NuZ5uF0MHtJ54nMc+79t/NR9GAmmaY3vUJu7fZyvww0=

 

[Jon Skeet [C# MVP]]

Have a symmetric encryption method that returns a base64 string. I then get
the hex representation of that string with the code below

public static string Base64ToHex(string input)
{
StringBuilder sb = new StringBuilder();
byte[] inputBytes = Encoding.UTF8.GetBytes(input);

foreach(byte b in inputBytes)
{
sb.Append(string.Format("{0:x2}", b));
}

return sb.ToString();
}

My question is: How do I get the hex string back to base64 string?

Ex.
base64: NuZ5uF0MHtJ54nMc+79t/NR9GAmmaY3vUJu7fZyvww0=
hexfrombase64: 4e755a357546304d48744a35346e4d632b3739742f4e523947416d6d6159
3376554a7537665a79767777303d
base64fromhex: NuZ5uF0MHtJ54nMc+79t/NR9GAmmaY3vUJu7fZyvww0=

Well, you can use Byte.Parse, or do it manually fairly easily. I have
to ask though - why are you converting into base64 and then into hex?
Why not just convert it from the binary (which is the natural low-down
result of the encryption) into hex in the first place, if you
absolutely need hex?

 

[Jon Skeet [C# MVP]]

Have a symmetric encryption method that returns a base64 string. I then get
the hex representation of that string with the code below

public static string Base64ToHex(string input)
{
StringBuilder sb = new StringBuilder();
byte[] inputBytes = Encoding.UTF8.GetBytes(input);

foreach(byte b in inputBytes)
{
sb.Append(string.Format("{0:x2}", b));
}

return sb.ToString();
}

My question is: How do I get the hex string back to base64 string?

Ex.
base64: NuZ5uF0MHtJ54nMc+79t/NR9GAmmaY3vUJu7fZyvww0=
hexfrombase64: 4e755a357546304d48744a35346e4d632b3739742f4e523947416d6d6159
3376554a7537665a79767777303d
base64fromhex: NuZ5uF0MHtJ54nMc+79t/NR9GAmmaY3vUJu7fZyvww0=

My previous answer was definitely somewhat suboptimal, I'm afraid.
Here's a method to actually do what you want.

Note that because you used UTF-8 and everything in Base64 is within the
ASCII character set, we don't need to do any conversion beyond casting
the hex value to a char. (Nor did you need to for your conversion,
btw.)

It could certainly be faster, but it'll do you fine, I'm sure:

static int ParseHexDigit(char c)
{
if (c >= '0' && c <= '9')
{
return c-'0';
}
if (c >= 'a' && c <= 'f')
{
return c-'a'+10;
}
if (c >= 'A' && c <= 'F')
{
return c-'A'+10;
}
throw new ArgumentException ("Invalid hex character");
}

public static string ParseHex(string hex)
{
char[] result = new char[hex.Length/2];

int hexIndex=0;
for (int i=0; i < result.Length; i++)
{
result = (char)(ParseHexDigit(hex[hexIndex++])*16+
ParseHexDigit(hex[hexIndex++]));
}
return new string (result);
}

 

[Jon Skeet [C# MVP]]

In some cases I need to have the encrypted string as querystring parameter
and some of the base64 charachers doen't go well in a url. I tried to
urlencode but it just get wrong. So I thougth I would convert it to a hex
string instead, that is url friendly.

Then I would suggest going straight from byte array to hex then, rather
than using Base64 encoding. Alternatively, something I've used
successfully in the past is a variation on Base64 which uses a URL-
friendly set of symbols. You could just use the existing Base64 methods
and then replace the dodgy characters, or you could write your own
Base64 methods.

Thats the reason. You don't think you could show the whole method code?
Would really help out a lot.

See my other post.

 

[Joris Dobbelsteen]

result = (char)(ParseHexDigit(hex[hexIndex++])*16+
ParseHexDigit(hex[hexIndex++]));

<snip>

This would be rather unsafe IMHO...
I would rather make this:

char tmp;

tmp = (char)(ParseHexDigit(hex[hexIndex++])*16;
tmp += (char)(ParseHexDigit(hex[hexIndex++]);
result = tmp;

 

[Jon Skeet [C# MVP]]

result = (char)(ParseHexDigit(hex[hexIndex++])*16+
ParseHexDigit(hex[hexIndex++]));

<snip>

This would be rather unsafe IMHO...
I would rather make this:

char tmp;

tmp = (char)(ParseHexDigit(hex[hexIndex++])*16;
tmp += (char)(ParseHexDigit(hex[hexIndex++]);
result = tmp;

In C, you would be right - in C#, the order of everything is well-
defined. Assuming it's the ordering which is the reason you think it's
unsafe...