Intn returns a random number backed by `crypto/rand`.

NewSeedInt64Crypto creates an `int64` seed value for `math/rand`.

NewSeedInt64Time creates an `int64` seed value for `math/rand` based on `time.Now()`.

RandString returns a random string of length `length` using the supplied alphabet.

CryptoRandSource is a `crypto/rand` backed source that satisfies the `math/rand.Source` interface definition.