http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.openssl;

import java.io.IOException;

import org.bouncycastle.operator.OperatorCreationException;

public class PEMEncryptedKeyPair
{
    private final String dekAlgName;
    private final byte[] iv;
    private final byte[] keyBytes;
    private final PEMKeyPairParser parser;

    PEMEncryptedKeyPair(String dekAlgName, byte[] iv, byte[] keyBytes, PEMKeyPairParser parser)
    {
        this.dekAlgName = dekAlgName;
        this.iv = iv;
        this.keyBytes = keyBytes;
        this.parser = parser;
    }

    public PEMKeyPair decryptKeyPair(PEMDecryptorProvider keyDecryptorProvider)
        throws IOException
    {
        try
        {
            PEMDecryptor keyDecryptor = keyDecryptorProvider.get(dekAlgName);

            return parser.parse(keyDecryptor.decrypt(keyBytes, iv));
        }
        catch (IOException e)
        {
            throw e;
        }
        catch (OperatorCreationException e)
        {
            throw new PEMException("cannot create extraction operator: " + e.getMessage(), e);
        }
        catch (Exception e)
        {
            throw new PEMException("exception processing key pair: " + e.getMessage(), e);
        }
    }
}