Abstract: A method and system for embedding data covertly in a text document using character rotation encoding. A character that occurs in first and second occurrences is selected, where the first occurrence of the character is a reference character and the second occurrence of the character as a rotatable character. The rotational orientation of the rotatable character is altered to produce an altered character with a predetermined rotation with respect to the reference character, wherein the rotation represents the embedded covert data. A text document is formatted based on the altered character.

Abstract: A method of authenticating a user includes providing a user key to an authentication authority, providing a transmission message from the authentication authority in response to the user key, providing a secret message using the transmission message, displaying the secret message to the user using a display screen, and providing a user response to the authentication authority in response to the user observing the secret message.

Abstract: A method and system for embedding data covertly in a text document using character rotation encoding. A character that occurs in first and second occurrences is selected, where the first occurrence of the character is a reference character and the second occurrence of the character as a rotatable character. The rotational orientation of the rotatable character is altered to produce an altered character with a predetermined rotation with respect to the reference character, wherein the rotation represents the embedded covert data. A text document is formatted based on the altered character.

Abstract: A method and system for embedding covert data in a text document using space encoding. The space encoding changes the inter-word spacing and/or inter-character spacing within a text row to a particular format such that the data is essentially visually hidden in the text document.