Quantum teleportation has been performed (and successfully I belive) under lab conditions. It was a specially marked photon which was teleported between two lasers. Also, in terms of FTL transmissions, you may be thinking of Quantum Tunnelling which is being used today to build faster transistors. Quantum Tunneling is an effect where certain particles exceed c, and is visible in more than one place at a time.
Didn't have enough time to sift through all the posts to see if anyone has explained this, but some ppl have recently asked me about quantum devices and their susceptibility to eavesdropping. Eavesdropping is (dare I say it given our current knowledge of physics) *virtually* impossible to do on quantum channels of communication. Best way to explain the whys and hows would be to understand why its possible to eavesdrop on current day technology. Information today is transmitted in measurable physical properties of a signal. Classical physics allows eavesdropping to take place because the signal's properties can be measured by an external source without disturbing the system. This would not be entirely true according to Quantum Theory. Quantum theory applies to all physical objects regardless of size, however, funny things begin to happen when applied to small objects like subatomic particles. Quantum devices will use photons of light and abide by 'Heisenburg's Uncertainty Principle' whereby, an attempt to measure a quantum system will disturb it, resulting in incorrect or incomplete information about its original state. In other words, its original state cannot be accurately determined because the attacker would introduce errors in transmission which can be easily detected by the parties involved. So far, quantum key distribution systems that have been proposed rely upon the polarisation of photons. A sender will transmit a photon with a certain polarisation and the receiver will randomly choose a method of measurement (either rectilinear or diagonal) and make it public, but keep the result private. Any attempt to eavesdrop will change the polarisation of the particle making any measurments by the eavesdropper invalid. ---------------- Forgive me if this is all incorrect, I have yet to take a formal physics course.
Well, yes spread spectrum technology does offer several advantages over narrow band methods of communication, however the 802.11 standard did (and still does i think?) have several shortcomings. Namely, the WEP (Wired-line Equivilant Privacy) suggests using a 40bit symmetric cipher such as RC4. This is optional and only applies to data contained within frames and not the headers. Therefore, it is possible for someone to gather information about usage of access points such as caller, receiver, etc. Also, the amount of time it takes to brute force a 40 bit key space is sooo small nowadays, it offers very little protection. (note: most Breezecom products actually use LESS than 40bit keys) Another shortcoming is that the standard does not suggest specific key management schemes. This is left up to the vendor to figure out and implement. One other problem, separate from the standard is how vendors implement FHSS. Essentially, FHSS is a spreading technique in which the center frequency of a narrow band signal is shifted based upon the output of a psuedo random number generator. Often times insecure initialization vectors are used. Sorry for the sidetrack guys!
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Quantum teleportation has been performed (and successfully I belive) under lab conditions. It was a specially marked photon which was teleported between two lasers. Also, in terms of FTL transmissions, you may be thinking of Quantum Tunnelling which is being used today to build faster transistors. Quantum Tunneling is an effect where certain particles exceed c, and is visible in more than one place at a time.
Didn't have enough time to sift through all the posts to see if anyone has explained this, but some ppl have recently asked me about quantum devices and their susceptibility to eavesdropping. Eavesdropping is (dare I say it given our current knowledge of physics) *virtually* impossible to do on quantum channels of communication. Best way to explain the whys and hows would be to understand why its possible to eavesdrop on current day technology. Information today is transmitted in measurable physical properties of a signal. Classical physics allows eavesdropping to take place because the signal's properties can be measured by an external source without disturbing the system. This would not be entirely true according to Quantum Theory. Quantum theory applies to all physical objects regardless of size, however, funny things begin to happen when applied to small objects like subatomic particles. Quantum devices will use photons of light and abide by 'Heisenburg's Uncertainty Principle' whereby, an attempt to measure a quantum system will disturb it, resulting in incorrect or incomplete information about its original state. In other words, its original state cannot be accurately determined because the attacker would introduce errors in transmission which can be easily detected by the parties involved. So far, quantum key distribution systems that have been proposed rely upon the polarisation of photons. A sender will transmit a photon with a certain polarisation and the receiver will randomly choose a method of measurement (either rectilinear or diagonal) and make it public, but keep the result private. Any attempt to eavesdrop will change the polarisation of the particle making any measurments by the eavesdropper invalid. ---------------- Forgive me if this is all incorrect, I have yet to take a formal physics course.
Well, yes spread spectrum technology does offer several advantages over narrow band methods of communication, however the 802.11 standard did (and still does i think?) have several shortcomings. Namely, the WEP (Wired-line Equivilant Privacy) suggests using a 40bit symmetric cipher such as RC4. This is optional and only applies to data contained within frames and not the headers. Therefore, it is possible for someone to gather information about usage of access points such as caller, receiver, etc. Also, the amount of time it takes to brute force a 40 bit key space is sooo small nowadays, it offers very little protection. (note: most Breezecom products actually use LESS than 40bit keys) Another shortcoming is that the standard does not suggest specific key management schemes. This is left up to the vendor to figure out and implement. One other problem, separate from the standard is how vendors implement FHSS. Essentially, FHSS is a spreading technique in which the center frequency of a narrow band signal is shifted based upon the output of a psuedo random number generator. Often times insecure initialization vectors are used. Sorry for the sidetrack guys!