Are there any requirements for SQLCipher passphrase? For example, minimum and maximum number of symbols, invalid symbols, etc.
There are no requirements for a SQLCipher passphrase. By default SQLCipher keys undergo a key derivation process with 256000 iterations of PBKDF2-HMAC-SHA512 which is used to convert the passphrase to the encryption key used for the database. This helps protect against brute force and dictionary attacks. However, if an application wants to enforce a specific passphrase validation process it must implement that logic itself.