What is the name of an attack where the compromise of one key compromises the whole system?

Question

Consider the following: A whole system depends on the security of one private key and if this key is, for any reason, compromised, the whole system will be compromised.

What's a suitable name for such an attack?

Answer 1

The whole system depends on the security of one private key (..that gets..) compromised.
Give a suitable name for such an attack.

I would call this class of attacks: Master key compromise.

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Examples of such attacks (as asked in comment) include

• The master key is revealed to an attacker by physically stealing a backup copy, bribery or duress (obligatory XKCD) of a holder of the master key. Mitigations use safes, and/or k-out-of-m secret sharing.
• The adversary extracts the master key from a device holding it (the most obvious example of that is when the master key is in every device, which is not unseen). Mitigations include using security-certified device at least for master keys (HSMs, SAMs, Smart Cards). Method of extraction include
  • directly reading the memory/medium that stores the key,
  • examining memory where the device using the key copies it, perhaps temporarily (e.g. with a debugger, a JTAG port, exploitation of a buffer overflow vulnerability somewhere in the code..)
  • timing attack, (differential) power analysis and similar side-channel attacks (including fault attacks)
• Cryptanalytic attack or/and brute force attack, where a secret key (including private) is inferred from public material, like ciphertext, plaintext made available to an adversary, public key. Mitigation include using larger security parameters for master keys.

Answer 2

It is not an attack model while it is a security feature for a scheme. The adversary might be able to compromise these lack of secrecy by different attacks to obtain the master key and find other session keys. Take a look at this question. Definitions of secrecy