Most visual code authentication schemes in the literature have been shown to be vulnerable to relay attacks: the attacker logs into the victim's \account A" using credentials that the victim provides with the intent of logging into \account B". Visual codes are not human- readable and therefore the victim cannot distinguish between the codes for A and B; on the other hand, codes must be machine-readable in order to automate the login process. We introduce a new type of vi- sual code, the SAVVIcode, that contains an integrity-validated human- readable bitmap. With SAVVIcode, attackers have a harder time swap- ping visual codes surreptitiously because the integrity check prevents them from modifying or hiding the human-readable distinguisher.
['Jonathan Millican', 'Frank Stajano']
SAVVIcode: Preventing Mafia Attacks on Visual Code Authentication Schemes (Short Paper)