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> A single private key passphrase is all that stands between a bad guy and everyone's credit card information... Well I know I feel better... Where do you get

> A single private key passphrase is all that stands between a bad guy and everyone's credit card information... Well I know I feel better... Where do you get that from? They encrypt all of the CC info using the public key. You need the private key AND the private key passphrase -- and one of them isn't stored on a computer.

corford 14y ago
I'm pretty sure UnoriginalGuy understands that. What he says is correct, the attackers now have the private key file so all that prevents them from decrypting the CC data is the passphrase. They don't know what this is but they can try and brute force it which is why it's relevant to wonder what cipher the key uses, how many bits and how long, random and complicated the passphrase text is. Hopefully, they used 4096 bits and a random >20 char string as the passphrase. That combined with a standard cipher algorithm (DSA, RSA) should be enough to keep us safe.
- darkarmani 14y ago
  > What he says is correct, the attackers now have the private key file I will concede that this is highly likely, but they did not confirm that the private key was taken.
  - UnoriginalGuy 14y ago
    It is implied that it was taken. The IRC log said that they had taken it and since Linode is talking about the passphrase in their blog post, the implication there is that it was taken too. If the bad guys didn't have the private key then the passphrase is literally irrelevant to the discussion. Since they would have to break the primary cryptographic key rather than just the passphrase. A passphrase protects a private key file NOT the data. So why would Linode even bring it up?
    - darkarmani 14y ago
      > A passphrase protects a private key file NOT the data. So why would Linode even bring it up? I would bring it when discussing how I cryptographically secured sensitive data. Especially, when people might be confused and try to argue that they should have used pbkdf2 and not encrypted the information (because they were thinking about password hashes).
- ryan-c 14y ago
  Cracking even a 1024 bit RSA key would cost at least millions of dollars. Credit card numbers are not worth that much.
  - ig1 14y ago
    Tens of thousands of credit and debit cards, many of which are likely to be corporate cards with extremely high spending limits ?
    - dangrossman 14y ago
      Worth no more than $1 a card on the black market. It'd be cheaper to buy cards than to try to crack the key. There's more supply than demand for stolen card numbers.
      - ig1 14y ago
        That's because the black market for credit cards is a lemon market [1] - known good corporate cards are much more valuable. [1] https://en.wikipedia.org/wiki/The_Market_for_Lemons https://en.wikipedia.org/wiki/The_Market_for_Lemons
  - scott_karana 14y ago
    Nobody needs to crack the key: merely the keyphrase. Bruteforcing is relatively cheap.
mike-cardwell 14y ago
The private key shouldn't be on any machine that it isn't used on. If we assume that the key is used on that machine, and is password protected, and is used automatically, then the unencrypted key, or its password, must exist in memory, if not on disk. Perhaps they log in when the machine boots and manually enter the password once, so it is cached and can be used for repeat decryption processes. If the key is in memory, then a blackhat who knows what he's doing can get access to it.
- corford 14y ago
  This isn't a problem unique to Linode though. The same risk is present for every system that needs a password/passphrase to decrypt. This is why effective security (not absolute - which is impossible for any system that has to connect with other systems) can only be achieved through a layered approach. Linode layered pretty well: Hashed and salted passwords, isolated systems, encrypted CC database and passphrase protected decryption key with no written record of what that passphrase is. They didn't do a perfect job but then who does (or even can)?
UnoriginalGuy 14y ago
> Where do you get that from? The article and the IRC log. The IRC dude said flat out that the "bad guys" have the private key and the encrypted data. They also have made no claims that turned out to be untrue yet. The Blog post infers that the bad guys have the private key by talking about passphrases. Why are passphrases on the private key even a discussion topic unless the private key has fallen into "enemy" hands? Therefore the ONLY thing between them and unencrypted data is the passphrase protecting the private key.

corford 14y ago

I'm pretty sure UnoriginalGuy understands that. What he says is correct, the attackers now have the private key file so all that prevents them from decrypting the CC data is the passphrase. They don't know what this is but they can try and brute force it which is why it's relevant to wonder what cipher the key uses, how many bits and how long, random and complicated the passphrase text is. Hopefully, they used 4096 bits and a random >20 char string as the passphrase. That combined with a standard cipher algorithm (DSA, RSA) should be enough to keep us safe.

darkarmani 14y ago
> What he says is correct, the attackers now have the private key file I will concede that this is highly likely, but they did not confirm that the private key was taken.
- UnoriginalGuy 14y ago
  It is implied that it was taken. The IRC log said that they had taken it and since Linode is talking about the passphrase in their blog post, the implication there is that it was taken too. If the bad guys didn't have the private key then the passphrase is literally irrelevant to the discussion. Since they would have to break the primary cryptographic key rather than just the passphrase. A passphrase protects a private key file NOT the data. So why would Linode even bring it up?
  - darkarmani 14y ago
    > A passphrase protects a private key file NOT the data. So why would Linode even bring it up? I would bring it when discussing how I cryptographically secured sensitive data. Especially, when people might be confused and try to argue that they should have used pbkdf2 and not encrypted the information (because they were thinking about password hashes).
ryan-c 14y ago
Cracking even a 1024 bit RSA key would cost at least millions of dollars. Credit card numbers are not worth that much.
- ig1 14y ago
  Tens of thousands of credit and debit cards, many of which are likely to be corporate cards with extremely high spending limits ?
  - dangrossman 14y ago
    Worth no more than $1 a card on the black market. It'd be cheaper to buy cards than to try to crack the key. There's more supply than demand for stolen card numbers.
    - ig1 14y ago
      That's because the black market for credit cards is a lemon market [1] - known good corporate cards are much more valuable. [1] https://en.wikipedia.org/wiki/The_Market_for_Lemons https://en.wikipedia.org/wiki/The_Market_for_Lemons
- scott_karana 14y ago
  Nobody needs to crack the key: merely the keyphrase. Bruteforcing is relatively cheap.

mike-cardwell 14y ago

The private key shouldn't be on any machine that it isn't used on. If we assume that the key is used on that machine, and is password protected, and is used automatically, then the unencrypted key, or its password, must exist in memory, if not on disk. Perhaps they log in when the machine boots and manually enter the password once, so it is cached and can be used for repeat decryption processes. If the key is in memory, then a blackhat who knows what he's doing can get access to it.

corford 14y ago
This isn't a problem unique to Linode though. The same risk is present for every system that needs a password/passphrase to decrypt. This is why effective security (not absolute - which is impossible for any system that has to connect with other systems) can only be achieved through a layered approach. Linode layered pretty well: Hashed and salted passwords, isolated systems, encrypted CC database and passphrase protected decryption key with no written record of what that passphrase is. They didn't do a perfect job but then who does (or even can)?

UnoriginalGuy 14y ago

> Where do you get that from? The article and the IRC log. The IRC dude said flat out that the "bad guys" have the private key and the encrypted data. They also have made no claims that turned out to be untrue yet. The Blog post infers that the bad guys have the private key by talking about passphrases. Why are passphrases on the private key even a discussion topic unless the private key has fallen into "enemy" hands? Therefore the ONLY thing between them and unencrypted data is the passphrase protecting the private key.