How many attackers can compute 2^30 operations??

Hi,
I am a researcher student.
I have to evaluate the efficiency of a given MAC algorithm, in terms of
security.

My MAC is based on an keyed LFSR Hash function, with 60-bit output.
To find collisions by an exaustive search I have to compute 2^30 hash
operations(this knowledge is based on the Birthday Paradox).

I have read(Wang and others) that 2^30 is a practicable effort for an
attacker with adeguate capabilities.
My question is: how many possible attackers in the world have these
capabilities?
In other words, I have to fear lots of attackers or a little bit of
these?

Thank you all for your answers!

Adrianz
Received on Thu Sep 29 21:57:56 2005