String content = String.format(FORMAT, merchantId, timestamp, requestBody);
Signature signature = Signature.getInstance("SHA256withRSA");
byte[] publicKeys = Base64Utils.decodeFromString(publicKey);
X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(publicKeys);
PublicKey pubKey = KeyFactory.getInstance("RSA").generatePublic(x509EncodedKeySpec);
signature.initVerify(pubKey);
signature.update(content.getBytes(StandardCharsets.UTF_8));
String channelSignature = URLDecoder.decode("signatureDataFromPayKKa", StandardCharsets.UTF_8);
boolean verified = signature.verify(Base64Utils.decodeFromString(channelSignature))