ENHANCED: library(crypto): Retain the compact representation of strings.

ENHANCED: library(crypto): Retain the compact representation of strings.

This avoids the costly (in terms of space requirements!) conversion of
compact lists of characters to lists of integers, making hashing, HKDF,
encryption, decryption, signing and signature verification an order of
magnitude more efficient (primarily in terms of space, also in time).

This makes library(crypto) suitable to process also very large files.