What is the current security level of an algorithm? I was reading a paper of some years ago about a cryptography and a phrase got my attention.


  We want to ensure a security level of at least $2^{80}$


I know that $2^{80}$ was used as rule of thumb rule, that's probably why they wrote that sentence.

But reading this I think that $2^{100}$ may also be too low.
Considering for example the resource that a state like US can have what is a reasonable security level? 

EDIT:
I'm considering only the security level for a bruteforce attack, other algorithm can have a solution that require less computational force.
First of all: The security and the length of the key depends on the system you use. So e.g. RSA needs longer keys than AES-256 does, to ensure the same security.

Second: The level of security depends on the application and how secure it has to be. A important point here is: How long should it be secure. There are still security systems in use, that can be broken in days. That's however no problem when the information only has to be secure for some minutes/hours.

This question / answer about algorithms used for SSH keys on the Information Security site might also help you.