Public/Private key pair protection on Windows

Discussion in 'Computer Security' started by Thomas K, Mar 25, 2005.

  1. Thomas K

    Thomas K Guest

    Dear all,

    Anyone with good information regarding the protection of the key pair?


    Thomas K, Mar 25, 2005
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  2. Thomas K

    John Guest

    What you really might want to protect is the private part (no pun intended).

    imo a token, smart card or hsm is the best place for it.

    All else fails.

    John, Mar 25, 2005
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  3. If the private key does not have a "good" password associated with it and
    someone else has physical access to your machine, you are not well
    protected. Further since MS often leaves the key around in "cache" if you
    ever use your private key, you are not well protected.

    For best results, generate your private key in a token (2048 bits or more
    preferred) and NEVER
    export it to a Windows machine. Only insert the token in the USB port when
    you must and only as
    long as it must be there. Further, be certain that any buffering of the key
    by Windows is erased when you are done using the private key, i.e., close
    the session, or turn off the power for at least 20 seconds. This will
    minimize the chances that someone else will acquire access to your key or be
    able to tale end your sessions.
    Edward A. Feustel, Mar 25, 2005
  4. Thomas K

    John Guest

    Normal tokens do not allow the private key to be exported.

    John, Mar 25, 2005
  5. for rsa key-pair ... there is also specification for ecdsa, related thread
    reference with pointer to nist fips186-2 ecdsa PKI: the end

    because of various issues with pc vulnerabilities .... there is
    the EU FINREAD standard ... misc posts:

    .... where you have a separate unit connected to pc with display and
    keypad that directly talks to the token ... for accurately displaying
    transaction and safely entering a token's pin/password.

    use of hardware token addresses direct copying of the private key. EU
    FINREAD attempts to address a couple additional vulnerabilities:

    * various kinds of keyloggers capturing the token pin/password and
    being able to execute transactions while the token is connected w/o
    your knowledge. EU FINREAD has its own keybad for pin/password

    * virus corrupting the transaction where the screen displays some
    transaction supposedly to be digitally signed, but what gets sent to
    the token for signing is totally different. EU FINREAD has its own
    (small) display for presenting transaction (somewhat oriented towards
    financial transactions ... akin to what you might find a supermarket
    checkout counter).

    there is also a dual-use attack.

    digital signature infrastructure primarily is a mode from 3-factor
    authentication ...

    * something you know
    * something you have
    * something you are

    where the relying party succesfully validating the digital signature
    can assume that the originating party is in possession of the
    corresponding private key (aka "something you have" authentication).

    A digital signature authentication scheme may be a flavor of
    challenge/response (countermeasure for replay attacks) ... where the
    relying party transmits some random bits which the other end digitally
    signs and returns the digital signature. the relying party then
    validates the digital signature with the public key ... which is proof
    that the other end is in possession of the corresponding private key
    (aka "something you have" authentication).

    Some infrastructures have also looked at use of public/private key
    digital signatures to imply more than simple authentication ... aka
    that verification of a digital signature is equivalent to a human
    signature ... which not only implies "something you have"
    authentication, but also implies something similar to a human
    signature, aka implication of reading, understanding, approving,
    agreement, and/or authorization.

    A dual-use attack is when the same private key is used for both 1)
    authentication events where random bits (that are never viewed, read,
    or understood) are digitally signed and 2) human signature events
    where there isn't some additional additional proof that some human
    hasn't actually read, understood, arpproved, agreed, and/or authorized
    the related bits being digitally signed.

    So a dual-use attack is for some attacker, in a supposedly purely
    authentication operation, transmit some bits for digital signing that
    purports to be random ... when the bits actually can be interpreted to
    represent some obligation as in a human signing event. A possible
    analogy is in the MASH show where Radar is getting the col. to sign
    stuff where the col. isn't actually reading what he is signing.

    Part of the issue may be the semantic ambiquity with the term "digital
    signature" ... where the use of the word "signature" is automatically
    taken to imply some relation to "human signature" ... even tho
    "digital signature" can be commonly used in situations where there is
    no implication at all of the equivalent conditions for human signature
    (read, understood, approved, agreed, and/or authorized).

    somewhat unrelated, hardware tokens can also be considered somewhat a
    phishing countermeasure. A lot of phishing is social engineering,
    convincing people to perform electronic act that makes them vulnerable
    (divulging their userids and passwords and other information that
    enables things like account theft and/or id-theft ... where
    transactions and/or other obligations happen w/o the person's

    When a hardware token is also required, it is probably going to be
    somewhat more difficult to convince a victim to mail off their
    hardware token. It still doesn't eliminate the social engineering
    where the attacker convinces the victim to directly execute the
    transactions for the benefit of the crook (however, it does somewhat
    minimize the ability for the crook to do their own fraudulent
    transactions w/o the owner's knowledge).
    Anne & Lynn Wheeler, Mar 25, 2005
  6. Thomas K

    Thomas K Guest

    Thx for all the feedback !

    I'd also like to how how OS (MS OS) knows that a private key is associated
    to a certificated located in one of the personal crypto stores
    When double clicking a certificate, it reads "You have a private key that
    corresponds to thise certificate". How does the OS know that?


    Thomas K, Mar 25, 2005
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