3 ms·

And that's why we have 2FA on separate devices or even hardware tokens. They allow some security even if the computer isn't trusted, like protection against rep

And that's why we have 2FA on separate devices or even hardware tokens. They allow some security even if the computer isn't trusted, like protection against replay attacks at a minimum.

edejong 10y ago
If you do not trust your hardware, 2FA is of no use. All communication and display can be MITMed on the untrusted computer. It gives the appearance of a normal login, but the behavior of the trusted site or system is emulated. The real username, password and 2FA authentication token is only send to the target machine by the attacker.
- akvadrako 10y ago
  That's not true. It prevents replay attacks, as I said. More advanced tokens also do more. My bank uses a hardware token for signing transfers and other actions which can include a human readable message or part of the target account number, making MITM much harder.
  - edejong 10y ago
    I'd say the risk of replay attack is not proportional to the risk of authenticating and authorizing on a fully compromised machine. It's comparing a candle light with a blazing fire. A definition issue with regard to "token": I sincerely do not think a device with display and keyboard used to sign transactions can be called "token". I'd say something like: trusted signing processor. But then again, I'm not a security specialist.
    - akvadrako 10y ago
      Well the big issue is that it prevents future access to your account. Let's say you have a simple 2FA device (no screen) and are using online banking. First you login via a compromised machine. The attacker MITM'ed you, so can see your account. 1. The bank should require a confirmation with your token to send money. If you don't send anything, the attacker can't either. 2. In the future, after the logout timeout, you know the attacker can't even read your account. It greatly reduces the attack surface you need to worry about. Any attack they do must be right then.
deleted 10y ago
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amelius 10y ago
How does 2FA protect against eavesdropping with something as simple as this: https://en.wikipedia.org/wiki/Hardware_keylogger https://en.wikipedia.org/wiki/Hardware_keylogger
- akvadrako 10y ago
  It doesn't of course - it protects your account from future access / replay attacks.

And that's why we have 2FA on separate devices or even hardware tokens. They allow some security even if the computer isn't trusted, like protection against replay attacks at a minimum.

edejong 10y ago

If you do not trust your hardware, 2FA is of no use. All communication and display can be MITMed on the untrusted computer. It gives the appearance of a normal login, but the behavior of the trusted site or system is emulated. The real username, password and 2FA authentication token is only send to the target machine by the attacker.

akvadrako 10y ago
That's not true. It prevents replay attacks, as I said. More advanced tokens also do more. My bank uses a hardware token for signing transfers and other actions which can include a human readable message or part of the target account number, making MITM much harder.
- edejong 10y ago
  I'd say the risk of replay attack is not proportional to the risk of authenticating and authorizing on a fully compromised machine. It's comparing a candle light with a blazing fire. A definition issue with regard to "token": I sincerely do not think a device with display and keyboard used to sign transactions can be called "token". I'd say something like: trusted signing processor. But then again, I'm not a security specialist.
  - akvadrako 10y ago
    Well the big issue is that it prevents future access to your account. Let's say you have a simple 2FA device (no screen) and are using online banking. First you login via a compromised machine. The attacker MITM'ed you, so can see your account. 1. The bank should require a confirmation with your token to send money. If you don't send anything, the attacker can't either. 2. In the future, after the logout timeout, you know the attacker can't even read your account. It greatly reduces the attack surface you need to worry about. Any attack they do must be right then.

deleted 10y ago

[deleted]

amelius 10y ago

How does 2FA protect against eavesdropping with something as simple as this: https://en.wikipedia.org/wiki/Hardware_keylogger https://en.wikipedia.org/wiki/Hardware_keylogger

akvadrako 10y ago
It doesn't of course - it protects your account from future access / replay attacks.