code: public static String getThumbprint(final X509Certificate cert) throws CertificateEncodingException {
  
  		if(cert == null)
  		{
  			return null;
  		}
  
  		byte[] rawOctets = cert.getEncoded();
  
  		SHA1Digest digest = new SHA1Digest();
  
  		byte[] digestOctets = new byte[digest.getDigestSize()];
  
  		digest.update(rawOctets, 0, rawOctets.length);
  
  		digest.doFinal(digestOctets, 0);
  
  		return new String(Base64.encode(digestOctets));
  	}
docs: Generates a SHA1 thumbprint of a certificate for long-term mapping.
  @param cert
  @return
  @throws java.security.cert.CertificateEncodingException