Which poses a greater risk, a sparse hash mapping or a high collision rate? When is one preferable over the other? What is the difference between an encoding, encryption, and hash? Which is stronger,...

Which poses a greater risk, a sparse hash mapping or a high collision rate?

When is one preferable over the other?

What is the difference between an encoding, encryption, and hash?

Which is stronger, a one-time pad with a 128-bit random number generator, or a 128-bit encryption algorithm such as IDEA, RC2, SEED, or

Twofish?