Encryption in Samsung Galaxy S8
When your device is encrypted (out of the box) and doesn't have a password, it means that - It is encrypted using the OEM encryption algorithm and the hardware characteristics specific to your device (see Trusted Execution Environment ). However, because there is no PIN / pattern lock , one can boot into your device and access data

When you create a PIN/ pattern to permit access to your device, this PIN is used to salt the encryption password and effectively change it. Hence PIN / pattern not only changes your encryption password but also prevents unauthorised access to your device. Everytime you change PIN/ pattern the encryption password is changed