| Man-in-the-middle Attack |
Website Links For Attack |
Information AboutMan-in-the-middle Attack |
| CATEGORIES ABOUT MAN-IN-THE-MIDDLE ATTACK | |
| cryptographic attacks | |
|
THE NEED FOR AN ADDITIONAL TRANSFER OVER A SECURE CHANNEL With the exception of the Interlock Protocol , all cryptographic systems that are secure against MITM '''attacks''' require an additional exchange or transmission of information over some kind of Secure Channel . Many Key Agreement methods with different security requirements for the secure channel have been developed. POSSIBLE SUBATTACKS The MITM attack may include one or more of:
MITM is typically used to refer to active manipulation of the messages, rather than passively Eavesdropping . EXAMPLE OF A SUCCESSFUL MITM ATTACK AGAINST PUBLIC-KEY ENCRYPTION Suppose Alice wishes to communicate with Bob. Meanwhile, Mallory wishes to eavesdrop on the conversation, or possibly deliver a false message to Bob. To get started, Alice must ask Bob for his Public Key . If Bob sends his public key to Alice, but Mallory is able to intercept it, a man-in-the-middle attack can begin. Mallory sends a forged message to Alice that claims to be from Bob, but includes Mallory's public key. Alice, believing this public key to be Bob's, then encrypts her message with Mallory's key and sends the enciphered message back to Bob. Mallory again intercepts, deciphers the message, keeps a copy, and reenciphers it (after alteration if desired) using the public key Bob originally sent to Alice. When Bob receives the newly enciphered message, he will believe it came from Alice. This example shows the need for Alice and Bob to have some way to ensure that they are truly using each other's public keys, rather than the public key of an attacker. Otherwise, such attacks are generally possible, in principle, against any message sent using public-key technology. Fortunately, there are a variety of techniques that help defend against MITM attacks. DEFENSES AGAINST THE ATTACK The possibility of a man-in-the-middle attack remains a serious security problem, even for many public-key based Cryptosystem s. Various defenses against MITM attacks use authentication techniques that are based on:
The integrity of public keys must generally be assured in some manner, but need not be secret. Passwords and shared secret keys have the additional secrecy requirement. Public keys can be verified by a Certificate Authority , whose public key is distributed through a secure channel (for example, with a web browser or OS installation). Public keys can also be verified by a Web Of Trust that distributes public keys through a secure channel (for example by face-to-face meetings). See Key Agreement for a classification of protocols that use various forms of keys and passwords to prevent man-in-the-middle attacks. MITM IN QUANTUM CRYPTOGRAPHY MITM attacks are a potential problem in Quantum Cryptography as well. Recently, hybrid protocols (classical + quantum) have been proposed to deal with it, especially for the Three-stage Quantum Cryptography Protocol . [http://arxiv.org/abs/cs.CR/0605083 BEYOND CRYPTOGRAPHY MITM should be seen as a general problem resulting from the presence of intermediate parties acting as proxy for clients on either side. If they are trustworthy and competent, all may be well; if they are not, nothing will be. How can one distinguish the cases? By acting as proxy and appearing as the trusted client to each side, the intermediate attacker can carry out much mischief, including various attacks against the confidentiality or integrity of the data passing through it. A notable non-cryptographic man-in-the-middle attack was perpetrated by one version of a {Link without Title} . Another example of a non-cryptographic man-in-the-middle attack is the "Turing Porn Farm". Brian Warner says this is a "conceivable attack" that Spammer s could use to defeat CAPTCHA s. The spammer sets up a Pornographic Web Site where access requires that the user solves the CAPTCHAs in question. However, Jeff Atwood points out that this attack is merely theoretical -- there is no evidence that any spammer has ever built a "Turing Porn Farm". MITM IMPLEMENTATION EXAMPLES
SEE ALSO
EXTERNAL LINKS
|
|
|