Hence comes the definition at the top of the page because key length must be a natural number.

It used a 40-bit cipher, which, I mean, the key length may have been enough.

However, this could be countered by doubling the key length.

The key length may vary, but is generally 128 bits.

See the discussion on the relationship between key lengths and quantum computing attacks at the bottom of this page for more information.

He started by finding the key length, as above.

So you take 56-bit key times three would be your new key length.

The key length for unrestricted exports was raised to 56 bits in July.

This means that the key length could be 30, 15, 10, 6, 5, 3, 2, or 1 characters long.

It would in practice be necessary to try various key lengths close to the estimate.