EP0706699B1 - Method for resetting a blocked pin or a blocked password - Google Patents

Abstract

The invention provides for an extended PIN/password comprising substantially more positions than the simple one with, for example, four positions. This extended PIN/password is used to unblock PINs/passwords blocked owing to excessive false attempts or loss and make them usable. The knowledge of the extended PIN/password allows the individual user to recover the use of his usual PIN/password without the aid of a specially authorised person or institution and thus have access to protected data and equipment.

Description

The invention relates to a method for removing the blocking of access to devices, data and other devices to which access can be achieved by entering a personal identification number, the so-called PIN or a password, according to the preamble of claim 1.

Many devices that contain protected data or functions, or special items of value, can be opened for the user via the personal identification number, the so-called PIN or a password, and can then be used. As an example of such devices, only cash dispensers at banks, or protected files in computer networks or other devices worth protecting are to be referred to here. The range of applications is wide.

As a rule, a PIN has so few digits, four are usual that they can be memorized. This also applies to a password. The PIN usually actually consists of single digits, while a password can consist of letters or a combination of letters and numbers.

In practice it happens again and again that the PIN or the password is entered incorrectly, either because you have not kept it correctly or because you make a typing mistake. In order to protect the content of the device or the integrity of the data, only a few failed attempts, for example three, are permitted. If the error counter has reached a predetermined value, the device or the file is blocked, so that even when using the correct PIN or the correct password, you no longer have access. The PIN or password is then to be regarded as blocked. However, there are also cases where a timely successful one Try to reset the error counter and there is the possibility to refill the counter up to the specified maximum.

If access to a device, a file or a process is blocked because the PIN itself or the password is blocked because the failed attempts have been exceeded, it is extremely difficult to gain access again. The user himself cannot unlock the locked device or reactivate the PIN or password. A special privileged person must perform the unlocking for this process. In practice, this is often extremely tedious and time-consuming.

Unlocking only by a specially authorized person is according to IBM Technical Disclosure Bulletin, Vol. 28, No. April 11, 1986, pages 5076-5077: "Pin check control for transaction terminal" not necessary. If the PIN is blocked (for example after 3 incorrect entries), the user can unlock it by entering the correct PIN twice in succession. When a thief simply tries out possible combinations, entering the correct PIN does not lead to the unlocking of a card that has been blocked due to previous failed attempts.

It is an object of the present invention to provide a method by which the individual user can himself unlock the device or regenerate the function of the PIN or the password himself. It should not be necessary to use a special privileged person for this.

This object is achieved in the method according to the preamble of claim 1 in that an extended PIN / extended password is provided, the extended PIN / the extended password for each individual user, preferably together with the normal simple one PIN / password is announced, the extended PIN / password is entered to remove the block and that this entry of the extended PIN / password is made by the individual user himself.

Advantageous further developments of the method according to the invention are laid down in the subclaims. The resulting advantages are obvious or are explained in more detail in the specific description below.

According to the invention, the locked user is given the opportunity to unlock the device himself by means of an extended PIN or by means of an extended password. In other words, the function of the normal PIN is controlled by the Users themselves restored by entering the extended PIN. In the following, the expression PIN will also be used for the expression password to keep the presentation easier. The invention thus has the considerable advantage of a much simpler procedure for unlocking the PIN or the password.

The extended PIN provided according to the invention is advantageously equipped with significantly more digits. The user can therefore usually not memorize them. For various reasons, it is particularly expedient to make the extended PIN usable only when the device is blocked, for example after the predetermined number of failed attempts with the simple PIN has been reached. Both PINs are made known to the individual user; he himself must ensure that they are kept securely. This applies in particular to the extended PIN, which is only used in extreme cases when the simple PIN can no longer be used, either because it has been lost or because the specified number of failed attempts has been reached.

After an expedient design of the extended PIN, it has a specific relationship to the simple PIN. For example, the last four digits of the extended PIN can be the same as the four-digit simple PIN.

According to an expedient embodiment according to the invention, which maintains the protection of the functions and data even after repeated regeneration, it is provided that after a certain number of failed attempts with the extended PIN, a new, extended blocking status is entered. Even then, the device or the function cannot be used. However, you can only get out of this extended blocking status, which should generally occur very rarely, only with the help of a privileged user who is authorized to clear this state.

A simple mathematical security analysis shows that the extended PIN, which has significantly more digits than the simple PIN, means that the security is approximately the same in both cases. This is explained below.

With an n-digit PIN in the decimal system and c permitted failed attempts and an m-digit extended PIN with d further permitted failed attempts, the probability of accidental opening is until the lock $${\text{w1 = c / (10}}^{\text{n}}\text{).}$$

Regenerating with the m-digit extended PIN and also three permitted failed attempts opens the following new possibility of random opening: $${\text{w2 = d / (10}}^{\text{m}}\text{).}$$

The total chance of random opening is now $${\text{w}}_{\text{total}}\text{= w1 + w2.}$$

Since the extended PIN has significantly more digits than the simple one, the following results: $${\text{w}}_{\text{total}}\text{∼ w1.}$$

The advantages of the invention can generally be seen in the fact that the individual user has the option of unlocking the locked device himself. Although this possibility is given, the security against unauthorized use practically does not decrease, as the above mathematical analysis shows. On the other hand, the organizational effort that would be required by a privileged system administrator to unlock the security-sensitive device would be considerably less and less, since the system administrator is only required in cases of the blocked extended PIN.

In mass applications of devices such. B. chip cards, and unlocking of individual areas on this chip card Entering PIN, the regeneration option for blocked cards introduced by the present invention is of particular importance.

An example of such a mass application can be a medical chip card for diabetics, which is protected with a four-digit PIN. The patient received this PIN in a so-called PIN letter, ie in a closed envelope, as is also the case with the PIN for the Euro check cards. This envelope also contains the extended PIN, for example with ten digits. This PIN letter is kept in a safe place and the patient memorizes the four-digit PIN. With this four-digit PIN, the patient is allowed access to the chip card.

If the patient is absent-minded or mistypes for other reasons, the card will block after five failed attempts, for example. In order to prevent misuse, the patient would have to go to an authorized authority to have the card unlocked again. This authority, for example a health insurance company, has the authority to unlock the cards. To do this, the identity of the cardholder must be carefully checked. On the other hand, the instance, the health insurance company, cannot read the medical data on the card. This ensures that it is the rightful owner of the card to be unlocked and that data protection is not violated.

The present invention opens up the possibility of regenerating the card without having to visit the authorized entity, such as the health insurance company in the present example. Either the patient himself has a personal computer with a chip card reader at home, where he, as a diabetic, enters his self-monitoring data on the chip card at home, or he goes to the family doctor and regenerates his card himself using the extended PIN that has now been selected.

Only when the number of attempts to unlock using the extended PIN has failed will the card be finally locked and can only be officially unlocked by the authorized authority.

• w1 = 5 : 10 000, also w1 = 0,0005
• w2 = 8 : 10 000 000 000, also w2 = 0,000 000 0008.

The question of security or the increase in uncertainty can be illustrated using the following example: Suppose the first counter, which is responsible for the normal, simple, e.g. four-digit PIN, blocks five attempts and the second counter, which registers the regeneration processes, which done with the extended PIN, blocks eight attempts, then the following calculation results:

• w1 = 5: 10,000, i.e. w1 = 0.0005
• w2 = 8: 10,000,000,000, i.e. w2 = 0,000,000,0008.

und damit $${\text{w}}_{\text{ges}}\text{∼ 0,0005.}$$

The total probability of accidental opening or access is now $${\text{w}}_{\text{total}}\text{= w1 + w2}$$

and thus $${\text{w}}_{\text{total}}\text{∼ 0.0005.}$$

As this example shows, the increase in uncertainty due to the extended PIN is negligible.

Claims (5)

1. A procedure for the unblocking of access to devices, data and other devices to which access can be achieved by entering a personal identification number, the so-called PIN, or a password, where access is blocked after a certain, pre-set number of failed attempts or where access is not possible if the PIN has been lost,
   characterised by the following steps:

   a) provision of an extended PIN or password;

   b) notification of each individual user of the extended PIN or password, preferably together with the normal, basic PIN or password;

   c) input of the extended PIN or password to remove the block, and

   d) input of the extended PIN or password by the individual user himself.
2. A procedure in accordance with Claim 1 characterised by the fact that the extended PIN or password has substantially more characters (preferably ten) than the normal, basic PIN or password which normally has four characters.
3. A procedure in accordance with Claims 1 or 2 characterised by the fact that the extended PIN or password is in a fixed relationship to the normal, basic PIN or password, in particular that the last four characters of an extended PIN or password are the same as the normal, basic four-character PIN or password.
4. A procedure in accordance with one of the preceding Claims characterised by the fact that the number of possible attempts to remove the block on access by means of the extended PIN or password is limited, in particular to five failed attempts, and that after this number has been reached a new extended-block status is attained.
5. A procedure in accordance with one of the preceding Claims characterised by the fact that the extended PIN or password is not usable or effective unless access by the basic PIN or password is blocked.