4 ms·

Interesting point - it's essentially a long lived secret. Actually what would happen if [large_comapny] had their TOTP secret revealed? Would they be forced to

Interesting point - it's essentially a long lived secret. Actually what would happen if [large_comapny] had their TOTP secret revealed? Would they be forced to invalidate everyones TOTP? They can't just disable it they would have to somehow authenticate you a third way....

tialaramex 7y ago
It's not one secret, it's a secret per pair. Imagine Anne and Barry both use TOTP with Google and Facebook, there would be one secret for (Anne,Google), one for (Anne,Facebok), one for (Barry,Google) and one for (Barry,Facebook). A good implementation chooses the secret randomly. But both sides need to know what it is. In the example above Anne needs to know both her secrets (they'd be inside her Google Authenticator) and Facebook needs to know both their secrets (probably in a SQL database). Stealing Facebook backups would get me the (Anne,Facebook) and (Barry,Facebook) secrets, but not the Google ones.
- penagwin 7y ago
  I know the client key is derived from the server key (So if Facebook's was released, your Google's TOTP is still safe). I'm guessing it depends on the implementation, are the server secrets normally derived per user or shared across users (Talking about just a single service such as facebook)?
  - tialaramex 7y ago
    > I know the client key is derived from the server key No. TOTP is a shared secret system, there is only one key. > I'm guessing it depends on the implementation, are the server secrets normally derived per user or shared across users Again no. The only reasonable thing to do is pick secrets entirely at random for each user. If the same secret is used then users can trivially impersonate each other, which makes no sense.
throw0101a 7y ago
> Actually what would happen if [large_comapny] had their TOTP secret revealed? Would they be forced to invalidate everyones TOTP? Yes. RSA got hacked for their SecurID information, so that the attackers could then turn around and get into Lockheed Martin: * https://gcn.com/articles/2011/06/07/rsa-confirms-tokens-used-to-hack-lockheed.aspx https://gcn.com/articles/2011/06/07/rsa-confirms-tokens-used... * https://www.scmagazine.com/home/security-news/rsa-confirms-lockheed-hack-linked-to-securid-breach/ https://www.scmagazine.com/home/security-news/rsa-confirms-l... Among other things, LM makes the F-35 fighter: * https://en.wikipedia.org/wiki/Lockheed_Martin https://en.wikipedia.org/wiki/Lockheed_Martin
- penagwin 7y ago
  Ooh that's interesting! Coincidentally my very close relative works for their F16 program! Yeah they're one of the largest military contractors - not a company anyone wants to have a breach.

tialaramex 7y ago

It's not one secret, it's a secret per pair. Imagine Anne and Barry both use TOTP with Google and Facebook, there would be one secret for (Anne,Google), one for (Anne,Facebok), one for (Barry,Google) and one for (Barry,Facebook). A good implementation chooses the secret randomly. But both sides need to know what it is. In the example above Anne needs to know both her secrets (they'd be inside her Google Authenticator) and Facebook needs to know both their secrets (probably in a SQL database). Stealing Facebook backups would get me the (Anne,Facebook) and (Barry,Facebook) secrets, but not the Google ones.

penagwin 7y ago
I know the client key is derived from the server key (So if Facebook's was released, your Google's TOTP is still safe). I'm guessing it depends on the implementation, are the server secrets normally derived per user or shared across users (Talking about just a single service such as facebook)?
- tialaramex 7y ago
  > I know the client key is derived from the server key No. TOTP is a shared secret system, there is only one key. > I'm guessing it depends on the implementation, are the server secrets normally derived per user or shared across users Again no. The only reasonable thing to do is pick secrets entirely at random for each user. If the same secret is used then users can trivially impersonate each other, which makes no sense.

throw0101a 7y ago

> Actually what would happen if [large_comapny] had their TOTP secret revealed? Would they be forced to invalidate everyones TOTP? Yes. RSA got hacked for their SecurID information, so that the attackers could then turn around and get into Lockheed Martin: * https://gcn.com/articles/2011/06/07/rsa-confirms-tokens-used-to-hack-lockheed.aspx https://gcn.com/articles/2011/06/07/rsa-confirms-tokens-used... * https://www.scmagazine.com/home/security-news/rsa-confirms-lockheed-hack-linked-to-securid-breach/ https://www.scmagazine.com/home/security-news/rsa-confirms-l... Among other things, LM makes the F-35 fighter: * https://en.wikipedia.org/wiki/Lockheed_Martin https://en.wikipedia.org/wiki/Lockheed_Martin

penagwin 7y ago
Ooh that's interesting! Coincidentally my very close relative works for their F16 program! Yeah they're one of the largest military contractors - not a company anyone wants to have a breach.