![]() The Kerberos authentication protocol includes some countermeasures. within that 'reasonable' limit, could succeed. The trade-off being that replay attacks, if they are performed quickly enough i.e. In networks that are unidirectional or near unidirectional, it can be an advantage. The advantages of this scheme are that Bob does not need to generate (pseudo-) random numbers and that Alice doesn't need to ask Bob for a random number. ![]() Timestamps are also implemented during mutual authentication, when both Bob and Alice authenticate each other with unique session IDs, in order to prevent the replay attacks. Bob only accepts messages for which the timestamp is within a reasonable tolerance. When Alice wants to send Bob a message, she includes her best estimate of the time on his clock in her message, which is also authenticated. For example, Bob periodically broadcasts the time on his clock together with a MAC. Synchronization should be achieved using a secure protocol. Timestamping is another way of preventing a replay attack. These can also be used during the authentication process to help establish trust between the two parties that are communicating with each other.īob can also send nonces but should then include a message authentication code (MAC), which Alice should check. They can be used to authenticate individual transactions in addition to sessions. One-time passwords are similar to session tokens in that the password expires after it has been used or after a very short amount of time. Eve can then replay her reply at a later time (when the previously predicted token is actually presented by Bob), and Bob will accept the authentication. Otherwise, Eve may be able to pose as Bob, presenting some predicted future token, and convince Alice to use that token in her transformation. Session tokens should be chosen by a random process (usually, pseudorandom processes are used). Bob would send a different session token, and when Eve replies with her captured value it will be different from Bob's computation so he will know it is not Alice. Now suppose an attacker Eve has captured this value and tries to use it on another session.If and only if both Alice’s and Bob’s values match, the login is successful.On his side Bob performs the same computation with the session token.For example, she would use the token to compute a hash function of the session token and append it to the password to be used. Bob sends a one-time token to Alice, which Alice uses to transform the password and send the result to Bob.The way of generating a session ID works as follows. Session IDs, also known as session tokens, are one mechanism that can be used to help avoid replay attacks. In this case, an attacker would be unable to perform the replay because on a new run the session ID would have changed. This works because a unique, random session ID is created for each run of the program thus, a previous run becomes more difficult to replicate. Due to the fact that there is no interdependency, there are fewer vulnerabilities. This combination of solutions does not use anything that is interdependent on one another. Replay attacks can be prevented by tagging each encrypted component with a session ID and a component number. After the interchange is over, Eve (acting as Alice) connects to Bob when asked for proof of identity, Eve sends Alice's password (or hash) read from the last session which Bob accepts, thus granting Eve access. Bob requests her password as proof of identity, which Alice dutifully provides (possibly after some transformation like hashing, or even salting, the password) meanwhile, Eve is eavesdropping on the conversation and keeps the password (or the hash). Suppose Alice wants to prove her identity to Bob. Alice (A) sends her hashed password to Bob (B). "an attack on a security protocol using a replay of messages from a different context into the intended (or original and expected) context, thereby fooling the honest participant(s) into thinking they have successfully completed the protocol run." Example Replay attacks are usually passive in nature.Īnother way of describing such an attack is: This is one of the lower-tier versions of a man-in-the-middle attack. This is carried out either by the originator or by an adversary who intercepts the data and re-transmits it, possibly as part of a spoofing attack by IP packet substitution. JSTOR ( December 2016) ( Learn how and when to remove this template message)Ī replay attack (also known as a repeat attack or playback attack) is a form of network attack in which valid data transmission is maliciously or fraudulently repeated or delayed.Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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