# What is total key space in transposition algorithms

How we can measure key space in transposition algorithms? Should we specify the method, like rail fence?

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In general the standard way to compute the effective key length of a cryptographic algorithm is as follows: we let $K$ denote the set of all possible keys for that algorithm; then the effective key length is $\lg |K|$, where $|K|$ denotes the size of the set $K$ and $\lg$ denotes the logarithm to base 2.