How do I deserlize XML to secured string to byte[]

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C#

XML :

<login>
  <user name="user" pwd="G,?????H
L`*?">

Property:

public byte[] pwd {
        get {
            return this.pwdField;
        }
        set {
            this.pwdField = value;
        }
    }

Throwing exception while setting the value to pwdField.

What I have tried:

Searched on google but not find any clue on it. Thank you