Unable to encode byte array to UTF8 then decode it back to bytes

Question

I'm trying to convert a byte array to a string, then at a later time convert those strings back to a byte array, but I'm getting some inconsistent results.

var salt = System.Text.Encoding.UTF8.GetString(encryptedPassword.Salt);
var key = System.Text.Encoding.UTF8.GetString(encryptedPassword.Key);
...
var saltBytes = System.Text.Encoding.UTF8.GetBytes(salt);
var keyBytes = System.Text.Encoding.UTF8.GetBytes(key);

In this case, the original salt and key are both byte[20], but the new ones are not equal (salt being a byte[36], key a byte [41], both with totally different values).

When I use what you have above my saltBytes == Salt and my keyBytes == Key. What happens in your ... code? What are your original values? — Lorek
– Lorek, Commented Sep 17, 2015 at 23:34
What are the contents of encryptedPassword.Salt and encryptedPassword.Key? Arbitrary bytes? That does not work; UTF8 has rules. You cannot expect arbitrary bytes to follow the UTF8 rules. — Dour High Arch
– Dour High Arch, Commented Sep 17, 2015 at 23:40
The contents are a salt and key generated from a Rfc2898DeriveBytes. — sds6065
– sds6065, Commented Sep 17, 2015 at 23:42

Jack A. · Accepted Answer · 2015-09-18 00:01:00Z

2

Basically what @DourHighArch said. You can go string->binary->string, but you can't expect to be able to go binary->string->binary using text encoding.

For what you are doing, you probably want to use something like base64 encoding. So you could write it like this:

var salt = Convert.ToBase64String(encryptedPassword.Salt);
var key = Convert.ToBase64String(encryptedPassword.Key);
...
var saltBytes = Convert.FromBase64String(salt);
var keyBytes = Convert.FromBase64String(key);

answered Sep 18, 2015 at 0:01

Jack A.

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1 Comment

sds6065 Over a year ago

Thanks for the explaination! Using base64 encoding is working and what I was intending to do.

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