fun signData(inputStr: String): String { val privateKeyEntry = getPrivateKey() val s = Signature.getInstance(SIGNATURE_SHA256withRSA) s.initSign(privateKeyEntry.privateKey) s.update(inputStr.toByteArray()) val signatureBytes = s.sign() val signatureString = Base64.encodeToString(signatureBytes, Base64.DEFAULT) return signatureString }