# Tag Info

To randomly guess a single key from a 128-bit key space has a chance of 1 divided by the number of elements or $\frac{1} {2^{128}}$ where $2^{128}$ is the number of keys possible. To get ballpark figures to convert between base 2 exponents and base 10 exponents you can use the following trick: Because $2^{10} = 1024 \approx 10^3$ you can easily count the ...
Yes, the problem of multicast one-way authentication can be solved using symmetric cryptography only, assuming (at least) one of the following applies (there might be other ways): we trust each receiving party to hold a common secret key secret, and not to use it nefariously; we accept overhead in the broadcast message growing linearly with the number $n$ ...