A clickable pyrrolopyrrole cyanine (PPCy) dye was synthesized by incorporating an alkyne moiety, followed by click reaction with azide-functionalized molecules of different polarities. The clickable dyes are readily amenable to labelling diverse molecules and exhibit an exceptionally high photostability and an impressive fluorescence quantum yield.

In this article, we’ve tried to examine the hypothesis of the robustness of a form by using CAPTCHA against CSRF and login CSRF attacks. Our investigations showed that unlike public opinion, common attacks to bypass CAPTCHAs such as Optical Character Recognition (OCR) and 3rd party human attacks are not applicable in the CSRF case and instead, Clickjacking is the most important scenario of CSRF...

A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a widely used security mechanism for constructing a high-confidence proof that the entity interacting with a remote service is actually a human being. Stimulated by the facts that: a) nowadays CAPTCHA challenges are solely based on the Latin alphabet, b) currently Internet population consists in its majori...

CAPTCHA is an important technology to prevent auto-script attack. Currently most of the CAPTCHA systems are text based, which firstly distort, rotate different characters and then use some obfuscation, aiming to make the text difficult to be recognized by autoscript while still can be learnt easily by real users. However, such kind of CAPTCHA schema either too simple, which can be attacked easi...

CAPTCHAs have become a standard security mechanism that are used to deter automated abuse of online services intended for humans. However, many existing CAPTCHA schemes to date have been successfully broken. As such, a number of CAPTCHA developers have explored alternative methods of designing CAPTCHAs. 3D CAPTCHAs is a design alternative that has been proposed to overcome the limitations of tr...

We propose a new construct, the Text-Graphics Character (TGC) CAPTCHA, for preventing dictionary attacks against password authentication systems allowing remote access via dumb terminals. Password authentication is commonly used for computer access control. But password authentication systems are prone to dictionary attacks, in which attackers repeatedly attempt to gain access using the entries...

The most common computer authentication method is to use alphanumerical usernames and passwords. This method has been shown to have significant drawbacks. For example, user tends to pick a passwords that can be easily guessed. On the other hand, if a password is hard to guess, then it is often hard to remember. In this paper, we conduct a comprehensive survey of the existing graphical password ...

Abuse of free Internet resources and services from false account creation, to spam, to identity theft, excessive bandwidth usage, or even vote stuffing online polls is a big problem. The Completely Automatic Public Turing Test to tell Computers and Humans Apart (CAPTCHA) controls access to resources but automated systems are increasingly adept at overcoming them. In this paper a method of acces...