# How does Truecrypt change password without the need for a complete re-encryption of volume

From what I understand:

1. TrueCrypt takes the password as message
3. calculates a digest
4. use digest for encryption

From what I understand. A good hash function

1. has Second pre-image resistance .i.e. It is difficult to find $m_2$ such that $m_1\neq m_2$ and $hash(m_1) = hash(m_2)$ .i.e. it is difficult to find a salt to produce the same digest

I observe that truecrypt can change my password in seconds (I assume the data is not reencrypted). How is this done while keeping the data on hard drive encrypted?

• it generates a volume key and encrypts that with the password? Aug 5, 2014 at 0:36
• I am not sure if that it how it works, but Truecrypt creates a volume key separate from the password. I assume it then encrypts the key using the password and stores it with the volume, so it can be decrypted then encrypted with a new password Aug 5, 2014 at 0:49
• For some background information, the actual encryption key is the one you see when it asks you to move around your mouse when you are setting up encryption. That key is encrypted with your password, as has been stated. Aug 8, 2014 at 13:55