Keytool - Problema ao importar certificado para o KeyStore

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

import javax.security.cert.CertificateException;
import javax.security.cert.X509Certificate;

public class CertificadoSSLLoader {

	public static X509Certificate load(String cerFileName) throws CertificateException {
		File file = new File(cerFileName);
		FileInputStream fis;
		try {
			fis = new FileInputStream(file);
		} catch (FileNotFoundException e) {
			throw new IllegalArgumentException("Arquivo " + cerFileName + " não existe.");
		}
		X509Certificate certificado = X509Certificate.getInstance(fis);
		return certificado;
	}
}

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.SignatureException;

import javax.security.cert.CertificateException;
import javax.security.cert.X509Certificate;

public class TestaValidadeCertificadoSSL {

	public static void main(String[] args) {
		try {
			X509Certificate certificado = CertificadoSSLLoader.load("certificado.cer");
				certificado.verify(certificado.getPublicKey());
		} catch (InvalidKeyException e) {
			System.out.println("Chave inválida.");
			e.printStackTrace();
		} catch (NoSuchAlgorithmException e) {
			System.out.println("Algoritmo inválido.");
			e.printStackTrace();
		} catch (NoSuchProviderException e) {
			System.out.println("Provedor inválido.");
			e.printStackTrace();
		} catch (SignatureException e) {
			System.out.println("Assinatura inválida.");
			e.printStackTrace();
		} catch (CertificateException e) {
			System.out.println("Ocorreu um erro ao carregar o certificado");
			e.printStackTrace();
		}
	}
}

Assinatura inválida.
java.security.SignatureException: Signature does not match.
	at sun.security.x509.X509CertImpl.verify(Unknown Source)
	at sun.security.x509.X509CertImpl.verify(Unknown Source)
	at com.sun.security.cert.internal.x509.X509V1CertImpl.verify(Unknown Source)
	at TestaValidadeCertificadoSSL.main(TestaValidadeCertificadoSSL.java:16)

abstract void verify(PublicKey key)  
    Verifies that this certificate was signed using the private key that corresponds to the specified public key.