Electrical computers and digital processing systems: support – System access control based on user identification by... – Solely password entry
Reexamination Certificate
1998-02-26
2001-01-23
Swann, Tod R. (Department: 2767)
Electrical computers and digital processing systems: support
System access control based on user identification by...
Solely password entry
C713S152000
Reexamination Certificate
active
06178508
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to computer security and, in particular, to systems in which encrypted information can be protected and maintained by multiple users using passwords.
BACKGROUND OF THE INVENTION
Many computer systems utilize some type of security to prevent unauthorized use. In the vast majority of systems this security takes the form of a single password per user for a particular company. The password is conventionally an arbitrary combination of characters known only to the user. The combination of characters is generally encoded in the system as a combination of bits and may be used to control login to the system as well as access to secure information in selected files.
In some systems, additional security is provided by requiring two or more users to act in concert in order to access secure information in files. In such systems, a group of users must all enter correct passwords in a single session in order to access the information. This type of operation is similar to the well-known protocols for the launching of nuclear weapons or financial documents which require two signatures (perhaps an employee and the employee's manager) to be valid.
A problem with such multiple user systems is that, if concerted action is needed for access to some information, there is a danger that one of the users required for concerted access to the file will forget his password or leave the company without telling anyone the password and thereby prevent the other remaining users from accessing the secured information. In many systems, it is possible to override the security system and obtain access to the information even if all users needed to access the information are not available. However, in cryptographic systems where the information is secured by encrypting it, it may not be possible to decrypt the information without all of the passwords. In addition, resources which require several users acting in concert are often cumbersome to use simply because it is often difficult to get all of the required users together in order to access the file.
One mechanism for avoiding these problems is to allow access to the secured information by a subset, or quorum, of the total group of users. For example, if there are five users, any two of the five users can concurrently enter passwords to access the secured data. Therefore, if one user forgets his password, leaves the company or is simply not available, a quorum can still be formed of the remaining users in order to access the data. This method works well with cryptographic systems because no special precautions need to be taken for lost or forgotten passwords.
In such a system, when a user name is entered, a password prompt would appear but two or more passwords would be required. Once the passwords were entered, one or more users could leave and let the remaining users work, or if the security constraints mandated, all users might be (administratively) required to remain present until the work was done and the passwords “cleared”. In either case, a user who left the company in possession of a valid password would find the password useless unless he could get the cooperation of other authorized users.
One problem with such quorum systems is that entry of the passwords can be cumbersome. Generally each user must enter his name and password. The passwords are then combined and the combination is checked against authorized combinations stored in an access file. However, if several users must enter passwords and the last person makes a mistake entering his password, then often all users must reenter their passwords.
Quorum systems also have problems with maintainability. For example, in order to change the size or composition of the possible groups, some method must be provided to obtain combinations of the passwords to form the quorum password combinations. Typically, all authorized users must reenter their passwords if a change is made to the size and composition of the quorum groups or if users are added or deleted.
Accordingly, there is a need for a security system which is useful for cryptographic systems, but can easily be maintained and can recover if passwords are forgotten. There is also a need for a security system in which the entry of passwords is simplified.
SUMMARY OF THE INVENTION
A secure system is achieved in accordance with the principles of the present invention by utilizing an unencrypted header file which is used to store a username and cryptographically hashed password for each of a plurality of authorized users. The passwords in the header file are cryptographically one-way hashed with a “salt value”, so as to not be reproducible by an unauthorized party. The salt value is a number which is typically unknown and can be the product of, for example, a random number generator. One-way hashing means that the actual password can not be recreated by an unintended party, even if the salt value were known. The cryptographically hashed passwords are never kept in an unprotected, or unhashed, state in memory, so are not vulnerable to access by an unintended party.
During use of the system, an authorized user must enter a password which, when hashed, can be found in the unencrypted header file. If the entered password is found in the file, the user is authorized access to the protected encrypted data.
Anyone gaining access to the unencrypted header file cannot obtain the passwords themselves. And, access to the encrypted data can not be gained without an authorized password.
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Darrow Justin T.
International Business Machines Corp.
Kudirka & Jobse LLP
Swann Tod R.
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