docs: public static byte[] rsPlainToAsn1(byte[] sign) {
  		if (sign.length != RS_LEN * 2) {
  			throw new CryptoException("err rs. ");
  		}
  		BigInteger r = new BigInteger(1, Arrays.copyOfRange(sign, 0, RS_LEN));
  		BigInteger s = new BigInteger(1, Arrays.copyOfRange(sign, RS_LEN, RS_LEN * 2));
  		ASN1EncodableVector v = new ASN1EncodableVector();
  		v.add(new ASN1Integer(r));
  		v.add(new ASN1Integer(s));
  		try {
  			return new DERSequence(v).getEncoded("DER");
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		}
  	}