Secret Word (English version)


This document tries to offer a solution for the problem of confidence in the process of payment between a Fon roaming user and a Bill user.

Fon is based on the principle to share bandwidth through Wi-Fi networks.3 main classes of Fon users exist: Linus, Bills and Aliens.

A Linus user can connect to any Fon access point using a username and a password. The Bills and Aliens users also, nevertheless will have to buy credits or time of use previously, through a Bill access point. This way, when a user looks for a Fon network, he will find first a Home page where its identification will be requested, and in case that it is not Linus, or he does not have present credit, he will have to introduce some type of payment means (VISA, Paypal…) In this document I will consider like Aliens the real Aliens as much as the Linus or Bills looking for roaming outside its house.

Here the problem arises that this document tries to approach. A user looking for roaming will get a page where a number of VISA or password is requested to him, nevertheless it does not know if this page is officially of a Bill, or is any other person that maliciously wants to collect numbers of VISA, Paypal codes, or users and passwords of Fon… How can I make sure that I am dealing with a confidence supplier through a Wi-Fi network?


The propose solution implies that the Alien previously has been registered in Fon. In case that the Alien has never been registered it will have to trust the current security certificate mechanism.

In case that the Alien (or the Linus/Bill) they have completed a brief registration form, this user will be able to use this mechanism of security. This form, among other things, will have to request a username and a “secret word” that will have to remember for the process of beginning of session (login).

Next I show a diagram describing this process:

1. The Alien finds a Fon access page, that requests its Fon username
a. If the Alien is not registered in Fon, jumps this step and enters through another link, without applying to this system
2. The Alien introduces its username.
3. The Web of the Bill gathers this username, and in addition it uses his own username and password to make a query against a Fon server.
4. Fon validates the username and password of the Bill, and keeps a registry from this consultation. If the Alien has been identified correctly it gives back his “secret word” to him.
5. The Alien will receive its secret word that will indicate that the access point that is using is an authorized supplier of Fon (Bill), besides to have registered in his Fon account the identifier of this Bill.
a. If it did not receive his secret word, the Alien would not have the certainty that the access point is valid, reason why would have to look for another one.
6. The Alien will finish its process of payment, providing its VISA or the system of payment that uses. In case of being a Linus or Alien with an active account, he will be able to introduce his password at this moment to finish the login process.


The mechanism that I describe offers the following advantages for the Alien:

1. It offers to him the guarantee of the access point is a Fon point, and not a phishing access point. A malicious user could copy easily a Fon Home page, and try to compile VISA cards on a very easy form, and being very difficult his identification. This mechanism identifies the supplier, doing more difficult a possible fraud.
2. A registry of the data and dates of the access point to which it has been connected. In his Fon profile it will be able to see which Bills has been connected and when.

Advantages for Fon:

1. Better way to guarantee the security to its potential users and to avoid the fraud using its name.
2. Mechanisms of monitoring of the Bills, Aliens
3. Aliens fidelization, since the registry of users in the Fon network is fomented.


The mechanism is not perfect from the point of view that in spite of this, own Bills can remain with our VISA and make fraudulent use of it. Nevertheless in the real world this also can happen, when doing a payment with VISA in any store runs the risk of being copied. The mechanism offers a form to identify to the supplier and to have the guarantee of which it is an authorized supplier. In case of badly use of your card, it will always be simpler to even identify to the thief knowing with whom you have made payments, and for Fon, the possibility to contrast data and to fight against the fraud.


This mechanism could be exported to any WiFi network community, from hot spots of Telephonic companies, to hotels and the Starbucks cafes. Nevertheless, in some scopes it has more feeling than in others. For example, an attack of phishing to a Starbucks network would be more difficult, since these ones only have presence within their own premises.

Another point where this mechanism could have sense could be Internet online stores, whose responsibility could be doubtful being a small supplier or not well-known. Creating a global system of authority that managed these “secret words” it could provide more confidence in these small stores.

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