* Dishonesty
* Deception
* Duplicity
* Hypocrisy
* Secretiveness
* Evasion
* Insincerity
* Dissembling
* Concealment
* Misrepresentation
The best antonym will depend on the specific context in which you are using the word. For example, if you are talking about someone's honesty, "dishonesty" would be a good antonym. If you are talking about someone's willingness to speak their mind, "secretiveness" might be a better choice.