How do I create a new backup of my phone with a NEW password since I don't know what my old one was?

Read: About encrypted backups in iTunes - Apple Support

In G0D We Trust wrote:

Can you tell me what other password that the average human being encounters cannot be reset if forgotten? My bank, my healthcare, my credit cards... all the biggest and most important ones. Yet I can't create a new password even when I create a new backup of my iPhone. This makes absolutely no sense.

And the NSA and the FBI are not complaining about how hard it is to access your health or banking data.

The TL;DR for AmishCake's link is that you will have to delete the back up from your computer and restore the phone as new.

The difference is your bank stores your ciphered password on their server. But the password for your backup isn't stored anywhere except in the backup itself. Apple doesn't know it by design, because if they did they would have to respond to a court order to decrypt it for police or other agencies. By making it impossible to bypass the password they protect your data from anyone who might might want to access it. But that puts the responsibility on you to use it wisely.

Personal responsibility? How dare you suggest such a thing!

gdgmacguy wrote:

Personal responsibility? How dare you suggest such a thing!

deggie already took me to task for that once today. 😉

Meg St._Clair wrote:

gdgmacguy wrote:

Personal responsibility? How dare you suggest such a thing!

deggie already took me to task for that once today. 😉

It's his birthday today, so be nice to him, or at least be forgiving of his chastising ways. 😉

There are several things that might help you figure it out:

• First, to make guessing faster, uncheck "Encrypt Backup" and you will be prompted for it immediately.
• You had to enter it (twice), so it is a password that you know, and if you are like most people, it is a password that you have used elsewhere.
• As the prompt would have come from iTunes, try Apple-related passcodes because you would have been in an Apple environment and it would probably be the first thing you would think of.
• Unless you take action to change it, it's the same password that you used the first time you ever backed up with Encrypt checked. So that could have been years ago.
• If you have a MS Exchange company account and there is an Exchange or company security profile in Settings/General/Profiles it might be your domain password in effect the first time you backed up after installing the exchange account.
• If you are desperate, Elcomsoft makes a password cracker for iPhone backups that is intended for use by law enforcement. It is priced accordingly. It is not guaranteed to work for really good, long passcodes. However, they have a trial version that will give you the first two characters of the passcode.