Evidence is pointing towards a bug inside the HTC smartphone...a bug that stops the app's 3 clickable menu options from being added to an Edittext's context menu (here associated with this app's Textbox field). This error has not been reported or reproducible in any other type of Android platform (so far).
When clicked these missing options individually permit: a help "file" to be displayed; easy erasure of Textbox; and display of the current character count in Textbox. Lack of these peripheral functions on your HTC device in no way impacts the integrity of the app's encryption and decryption algorithms.
Investigation into this problem continues.