There seems to be a confusion between crypt(3) and crypto(7) here.
The crypt function is defined in unistd.h and is used for password
and data encryption, while crypto is OpenSSL's library implementing
cryptographic algorithms used in Internet standards.

crypt  - https://www.unix.com/man-page/all/3C/crypt
crypto - https://www.openssl.org/docs/man1.1.1/man7/crypto.html