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"The process for encrypting a file: (3) SHA-256 hash the shared secret to generate a 64-bit IV."

"The process for decrypting a file: (4) Validate the IV against the shared secret hash and format version."

Does anyone else see a problem with the above? I do.

1. Isn't an IV supposed to be random, and definitely not derived from the plaintext?

2. The above comments about how crypto libraries should provide generic operations that always use the best possible cipher, like 'hash this for me', not 'SHA-256 this for me'.

IV seems way too short. However I'm not very familiar with Chacha20, so not sure if this is an issue.

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