public void setCipherService(CipherService cipherService) {
        this.cipherService = cipherService;
    }
Sets the {@code CipherService} to use for encrypting and decrypting serialized identity data to prevent easy
inspection of Subject identity data.
<p/>
If the CipherService is a symmetric CipherService (using the same key for both encryption and decryption), you
should set your key via the {@link #setCipherKey(byte[])} method.
<p/>
If the CipherService is an asymmetric CipherService (different keys for encryption and decryption, such as
public/private key pairs), you should set your encryption and decryption key via the respective
{@link #setEncryptionCipherKey(byte[])} and {@link #setDecryptionCipherKey(byte[])} methods.
<p/>
<b>N.B.</b> Unless overridden by this method, the default CipherService instance is an
{@link AesCipherService}.  This {@code RememberMeManager} implementation already has a configured symmetric key
to use for encryption and decryption, but it is recommended to provide your own for added security.  See the
class-level JavaDoc for more information and why it might be good to provide your own.

@param cipherService the {@code CipherService} to use for encrypting and decrypting serialized identity data to
                     prevent easy inspection of Subject identity data.
core/src/main/java/org/apache/shiro/mgt/AbstractRememberMeManager.java