Java Security

I had thought that a simple problem to create an SHA1 hash of password+salt would be easy to create and establish, however it is not working. I am suppose to create a security key that is the SHA1 hash of the password concatenated with the Salt (i.e. key = sha1hash(pass + salt);). The resultant hash should be encoded as a Base-16 string (without spaces or separator characters), that is two characters for each byte in the SHA1 hash.

import java.io.IOException;
import java.security.MessageDigest;
import java.security.SecureRandom;

public class TSecurityToken {
    private static final String passworddigest = "somepassworddigest";
    private static String hexits = "0123456789ABCDEF";

    public static String createdigest(byte[] salt, String entity) throws Exception {
        MessageDigest sha = MessageDigest.getInstance("SHA-1");
        sha.reset();
        sha.update(entity.getBytes());
        sha.update(salt);
        byte[] pwhash = sha.digest();             
        return toHex(concatenate(pwhash, salt));
    }
    
    private static byte[] concatenate(byte[] l, byte[] r) {
        byte[] b = new byte[l.length + r.length];
        System.arraycopy(l, 0, b, 0, l.length);
        System.arraycopy(r, 0, b, l.length, r.length);
        return b;
    }
    
    private static String toHex(byte[] block) {
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < block.length; ++i) {
            buf.append(hexits.charAt((block[i] >>> 4) & 0xf));
            buf.append(hexits.charAt(block[i] & 0xf));
        }
        return buf.toString();
    }

   public static final SecurityToken getSecurityToken(){
          SecruityToken token = new SecurityToken();
          try{
            SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
            byte[] salt = new byte[8];
            random.nextBytes(salt);
            token.setSalt(toHex(salt));
            token.setSecuritykey(createdigest(salt, passworddigest));
          }
          catch (Exception e){e.printStackTrace();}
          return token;
   }
}

public class SecurityToken{
    private String salt;
    private String securitykey;

    public void setSalt(String salt){
          this.salt = salt;
    }
    public String getSalt(){
          return salt;
    }
    public void setSecuritykey(String securitykey){
          this.securitykey= securitykey;
    }
    public String getSecuritykey(){
          return securitykey;
    }
}

The receipt that is receiving my password is based in .NET and thus I am unaware where exactly my code is going wrong. I want to know if I am creating my code incorrectly or something could be wrong on their end.