[ISN] Master Key Copying Revealed

From: InfoSec News (isnat_private)
Date: Thu Jan 23 2003 - 03:24:03 PST

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    Forwarded from: William Knowles <wkat_private>
    January 23, 2003  
    A security researcher has revealed a little-known vulnerability in
    many locks that lets a person create a copy of the master key for an
    entire building by starting with any key from that building.
    The researcher, Matt Blaze of AT&T Labs-Research, found the 
    vulnerability by applying his area of expertise - the security flaws 
    that allow hackers to break into computer networks - to the real-world 
    locks and keys that have been used for more than a century in office 
    buildings, college campuses and some residential complexes.
    The attack described by Mr. Blaze, which is known by some locksmiths, 
    leaves no evidence of tampering. It can be used without resorting to 
    removing the lock and taking it apart or other suspicious behavior 
    that can give away ordinary lock pickers.
    All that is needed, Mr. Blaze wrote, is access to a key and to the 
    lock that it opens, as well as a small number of uncut key blanks and 
    a tool to cut them to the proper shape. No special skills or tools are 
    required; key-cutting machines costing hundreds of dollars apiece make 
    the task easier, but the same results can be achieved with a simple 
    metal file.
    After testing the technique repeatedly against the hardware from major 
    lock companies, Mr. Blaze wrote, "it required only a few minutes to 
    carry out, even when using a file to cut the keys."
    AT&T decided that the risk of abuse of the information was great, so 
    it has taken the unusual step of posting an alert to law enforcement 
    agencies nationwide. The alert describes the technique and the 
    possible defenses against it, though the company warns that no simple 
    solution exists.
    The paper, which Mr. Blaze has submitted for publication in a computer 
    security journal, has troubled security experts who have seen it. Marc 
    Weber Tobias, a locks expert who works as a security consultant to law 
    enforcement agencies, said he was rewriting his police guide to locks 
    and lock-picking because of the paper. He said the technique could 
    open doors worldwide for criminals and terrorists. "I view the problem 
    as pretty serious," he said, adding that the technique was so simple, 
    "an idiot could do it."
    The technique is not news to locksmiths, said Lloyd Seliber, the head 
    instructor of master-key classes for Schlage, a lock company that is 
    part of Ingersoll-Rand. He said he even taught the technique, which he 
    calls decoding, in his training program for locksmiths.
    "This has been true for 150 years," Mr. Seliber said.
    Variations on the decoding technique have also been mentioned in 
    passing in locksmith trade journals, but usually as a way for 
    locksmiths to replace a lost master key and not as a security risk.
    When told that Mr. Seliber taught the technique to his students, Mr. 
    Tobias said: "He may teach it, but it's new in the security industry. 
    Security managers don't know about it."
    In the paper, Mr. Blaze applies the principles of cryptanalysis, 
    ordinarily used to break secret codes, to the analysis of mechanical 
    lock designs. He describes a logical, deductive approach to learning 
    the shape of a master key by building on clues provided by the key in 
    hand  an approach that cryptanalysts call an oracle attack. The 
    technique narrows the number of tries that would be necessary to 
    discover a master-key configuration to only dozens of attempts, not 
    the thousands of blind tries that would otherwise be necessary.
    The research paper might seem an odd choice of topics for a computer 
    scientist, but Mr. Blaze noted that in his role as a security 
    researcher for AT&T Labs, he examined issues that went to the heart of 
    business security wherever they arose, whether in the digital world or 
    the world of steel and brass.
    Since publishing Mr. Blaze's technique could lead to an increase in 
    thefts and other crimes, it presented an ethical quandary for him and 
    for AT&T Labs  the kind of quandary that must also be confronted 
    whenever new security holes are discovered in computing.
    "There's no way to warn the good guys without also alerting the bad 
    guys," Mr. Blaze said. "If there were, then it would be much simpler  
    we would just tell the good guys."
    Publishing a paper about vulnerable locks, however, presented greater 
    challenges than a paper on computer flaws.
    The Internet makes getting the word out to those who manage computer 
    networks easy, and fixing a computer vulnerability is often as simple 
    as downloading a software patch. Getting word out to the larger, more 
    amorphous world of security officers and locksmiths is a more daunting 
    task, and for the most part, locks must be changed mechanically, one 
    by one. 
    But Mr. Blaze said the issue of whether to release information about a 
    serious vulnerability almost inevitably came down to a decision in 
    favor of publication.
    "The real problem is there's no way of knowing whether the bad guys 
    know about an attack," he said, so publication "puts the good guys and 
    the bad guys on equal footing."
    In this case, the information appears to have made its way already to 
    the computer underground. The AT&T alert to law enforcement officials 
    said that a prepublication version of the paper distributed privately 
    by Mr. Blaze for review last fall had been leaked onto the Internet, 
    though it has not been widely circulated.
    "At this point we believe that it is no longer possible to keep the 
    vulnerability secret and that more good than harm would now be done by 
    warning the wider community," the company wrote.
    There is evidence that others have chanced upon other versions of the 
    technique over the years. Though it does not appear in resources like 
    "The M.I.T. Guide to Lockpicking," a popular text available on the 
    Internet, Mr. Blaze said, "several of the people I've described this 
    to over the past few months brightened up and said they had come on 
    part of this to make a master key to their college dorm."
    Mr. Blaze acknowledged that he was only the first to publish a 
    detailed look at the security flaw and the technique for exploiting 
    "I don't think I'm the first person to discover this attack, but I do 
    think I'm the first person to work out all the details and write it 
    down," he said. "Burglars are interested in committing burglary, not 
    in publishing results or warning people."
    Mr. Tobias, the author of "Locks, Safes and Security: An International 
    Police Reference," said that the technique was most likely to be used 
    by an insider  someone with ready access to a key and a lock. But it 
    could also be used, he said, by an outsider who simply went into a 
    building and borrowed the key to a restroom. 
    He said he had tested Mr. Blaze's technique the way that he tests many 
    of the techniques described in his book: he gave instructions and 
    materials to a 15-year-old in his South Dakota town to try out. The 
    teenager successfully made a master key.
    In the alert, AT&T warned, "Unfortunately, at this time there is no 
    simple or completely effective countermeasure that prevents 
    exploitation of this vulnerability, short of replacing a master-keyed 
    system with a nonmastered one."
    The letter added, "Residential facilities and safety-critical or 
    high-value environments are strongly urged to consider whether the 
    risks of master keying outweigh the convenience benefits in light of 
    this new vulnerability."
    Other defenses could make it harder to create master keys.
    Mr. Blaze said that owners of master-key systems could move to the 
    less popular master-ring system, which allows a master key to operate 
    the tumblers in a way that is not related to the individual keys. But 
    that system has problems of its own, security experts say.
    Mr. Blaze suggested that creating a fake master key could also be made 
    more difficult by using locks for which key blanks are difficult to 
    get, though even those blanks can be bought in many hardware stores 
    and through the Internet.
    But few institutions want to spend the money for robust security, said 
    Mr. Seliber of Schlage. His company recommends to architects and 
    builders that they take steps like those recommended by Mr. Blaze, 
    measures that make it more difficult to cut extra keys  like using 
    systems that are protected by patents because their key blanks are 
    somewhat harder to buy, Mr. Seliber said. Even though such measures 
    would add only 1 to 2 percent to the cost of each door, builders were 
    often told to take a cheaper route. He said that they were told, " 
    `We're not worried about ninjas rappelling in from the roof stuff  
    take it easy.' "
    That is not news to Mr. Blaze, who said it was also a familiar refrain 
    in the world of computer security. "As any computer security person 
    knows," he said, "in a battle between convenience and security, 
    convenience has a way of winning."
    "Communications without intelligence is noise;  Intelligence
    without communications is irrelevant." Gen Alfred. M. Gray, USMC
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