code: public static String getSignCertId() {
  		try {
  			Enumeration<String> aliasenum = keyStore.aliases();
  			String keyAlias = null;
  			if (aliasenum.hasMoreElements()) {
  				keyAlias = aliasenum.nextElement();
  			}
  			X509Certificate cert = (X509Certificate) keyStore
  					.getCertificate(keyAlias);
  			return cert.getSerialNumber().toString();
  		} catch (Exception e) {
  			e.printStackTrace();
  			LogUtil.writeErrorLog("getSignCertId Error", e);
  			return null;
  		}
  	}
docs: 获取配置文件acp_sdk.properties中配置的签名私钥证书certId
  
  @return 证书的物理编号