Secure Channel - Secure Channels in The Real World

Secure Channels in The Real World

There are no perfectly secure channels in the real world. There are, at best, only ways to make insecure channels (e.g., couriers, homing pigeons, diplomatic bags, etc.) less insecure: padlocks (between courier wrists and a briefcase), loyalty tests, security investigations, and guns for courier personnel, diplomatic immunity for diplomatic bags, and so forth.

In 1976, two researchers proposed a key exchange technique (now named after them) — Diffie–Hellman key exchange (D-H). This protocol allows two parties to generate a key only known to them, under the assumption that a certain mathematical problem (e.g., the Diffie–Hellman problem in their proposal) is computationally infeasible (i.e., very very hard) to solve, and that the two parties have access to an authentic channel. In short, that an eavesdropper—conventionally termed 'Eve', who can listen to all messages exchanged by the two parties, but who can not modify the messages—will not learn the exchanged key. Such a key exchange was impossible with any previously known cryptographic schemes based on symmetric ciphers, because with these schemes it is necessary that the two parties exchange a secret key at some prior time, hence they require a confidential channel at that time which is just what we are attempting to build.

It is important to note that most cryptographic techniques are trivially breakable if keys are not exchanged securely or, if they actually were so exchanged, if those keys become known in some other way — burglary or extortion, for instance. An actually secure channel will not be required if an insecure channel can be used to securely exchange keys, and if burglary, bribery, or threat aren't used. The eternal problem has been and of course remains — even with modern key exchange protocols — how to know when an insecure channel worked securely (or alternatively, and perhaps more importantly, when it did not), and whether anyone has actually been bribed or threatened or simply lost a notebook (or a notebook computer) with key information in it. These are hard problems in the real world and no solutions are known — only expedients, jury rigs, and workarounds.

Read more about this topic:  Secure Channel

Famous quotes containing the words secure, channels, real and/or world:

    The prosecution of [Warren] Hastings, though he should escape at last, must have good effect. It will alarm the servants of the Company in India, that they may not always plunder with impunity, but that there may be a retrospect; and it will show them that even bribes of diamonds to the Crown may not secure them from prosecution.
    Horace Walpole (1717–1797)

    People between twenty and forty are not sympathetic. The child has the capacity to do but it can’t know. It only knows when it is no longer able to do—after forty. Between twenty and forty the will of the child to do gets stronger, more dangerous, but it has not begun to learn to know yet. Since his capacity to do is forced into channels of evil through environment and pressures, man is strong before he is moral. The world’s anguish is caused by people between twenty and forty.
    William Faulkner (1897–1962)

    Here come real stars to fill the upper skies,
    And here on earth come emulating flies....
    Robert Frost (1874–1963)

    O, I have passed a miserable night,
    So full of fearful dreams, of ugly sights,
    That, as I am a Christian faithful man,
    I would not spend another such a night
    Though ‘twere to buy a world of happy days,
    So full of dismal terror was the time.
    William Shakespeare (1564–1616)