Only in your brain. Yith Library doesn’t store the master passwords. It is very important that you don't forget it because in this situation you won't be able to read your passwords and as Yith Library doesn't store the master password, it won't help you to reset it
No. The master password is only used locally in your browser.
The first time you add a password to Yith Library a master password will be asked, that’s when is set.
Yes. In the web client, under the advanced options, there is a button to change your master password.
We first use PBKDF2 (Password-Based Key Derivation Function 2) key derivation on the master password with 1000 iterations and a salt value. Then we use the AES algorithm in CCM (CTR mode with CBC MAC) mode with an initialization vector, a key size of 128 bits and a tag length of 64 bits.