public byte[] getCipherKey() {
        //Since this method should only be used with symmetric ciphers
        //(where the enc and dec keys are the same), either is fine, just return one of them:
        return getEncryptionCipherKey();
    }
Convenience method that returns the cipher key to use for <em>both</em> encryption and decryption.
<p/>
<b>N.B.</b> This method can only be called if the underlying {@link #getCipherService() cipherService} is a symmetric
CipherService which by definition uses the same key for both encryption and decryption.  If using an asymmetric
CipherService public/private key pair, you cannot use this method, and should instead use the
{@link #getEncryptionCipherKey()} and {@link #getDecryptionCipherKey()} methods individually.
<p/>
The default {@link AesCipherService} instance is a symmetric cipher service, so this method can be used if you are
using the default.

@return the symmetric cipher key used for both encryption and decryption.
core/src/main/java/org/apache/shiro/mgt/AbstractRememberMeManager.java