Secure CSPRNG's for cryptographic keys In reality, it is not practical for ciphers such as stream ciphers and AES to generate keys using a TRNG, so instead they have to use a CSPRNG. As an LFSR can generate pseudo random numbers,so can a LFSR be adapted so it can be used as CSPRNG, and what are the other ways to construct a CSPRNG.
LFSR as such isn't a CSPRNG. There are diverse CSPRNGs, see crypto textbooks, also A. Menezes et al., Handbook of Applied Cryptography (freely available online). I have a code for a CSPRNG based on RSA, see Ex. 5 in s13.zetaboards.com/Crypto/topic/7234475/1/