bits of entropy for master password(Secret Key) and AES-256 Bit,What is the difference ?

Sorry if my English is not completely correct.
I would like to know between bits of entropy for master password(including, Secret Key) and AES-256 Bit , How is it different In terms of the number of bits or the strength of the data encryption ?

I explain as follows,
secret key and master password used to encrypt-decrypt data, protect data in 1password. This is true that you guys describe.
Secret Key that adds 128 bits of entropy to strengthen my Master Password
Therefore, this case will say the strength of all 1password account users will be 128+(bits of master password).

Suppose I created a 20-digit of master password, (in the symbol group: All ASCII printable characters) It has an entropy number of 6.555 bits per 1 character. (I quote the number of bits from this: https://en.wikipedia.org/wiki/Password_strength ),
Therefore the number of bits to be received is 20x6.570 = 131.4 bits
Then, when combined with the bits of the secret key, it will be 128 + 131 = 259 bits.

This is what I would ask you,
259 bit strength that I got and 256 bit-AES,
1. Which is the most important thing to protect from an attack?
Of course, I don't know that any data decoding process,
2. The attacker will guess the strength part of my 259-bit (Received from the my master password and secret key)
Or in the aes-256 bit section directly?
3. An attacker has to use predictions. It is something that talks about exponents. Right? If yes it is 2^259 vs 2^256.

Comments

  • BenBen AWS Team

    Team Member

    Hi @sector

    Great questions. I've asked our security team if they can please chime in here. In the mean time, you may be interested in our Security Design White Paper.

    Thanks!

    Ben

  • BenBen AWS Team

    Team Member
    edited May 22

    @sector

    I've reviewed your questions with our security team and I have some answers to share.

    Suppose I created a 20-digit of master password, (in the symbol group: All ASCII printable characters) It has an entropy number of 6.555 bits per 1 character. > (I quote the number of bits from this: https://en.wikipedia.org/wiki/Password_strength ),
    Therefore the number of bits to be received is 20x6.570 = 131.4 bits
    Then, when combined with the bits of the secret key, it will be 128 + 131 = 259 bits.

    That would be the bits of entropy for your key. You're on the right track there. But then it sounds like you're trying to compare that to AES256? AES256 is the other component in the equation. If your Master Password + Secret Key are the key, then AES256 is the lock that the key operates. I'm not sure the two can really be compared in that way. They serve different purposes.

    Which is the most important thing to protect from an attack?

    A long unique Master Password is going to be your best defense. My colleague Daniel from our security team wrote about this in more detail here. Does that make sense? Please let me know.

    Ben

  • Thank you very much for the explanation, @Ben
    I can understand that bits of entropy for master password (and secret key) should not be compared to bits of AES-256, because the process these two things are different.
    And Daniel's second description from your security team,
    I can conclude that should create a master password that can give as many bits of entropy as my can remember and use easily.

    I therefore have additional questions and sections that have not been explained by him. Please leave a question to ask your security team too.

    Again, I'm no expert, just a user without any encryption skills.
    I just think about having fun. I want to ask from that suspicion.

    1. I would like to know In the event that someone tries to access the item data stored in my 1password.
      They have only one way is must computational effort to bits of entropy for my key (key is Master Password + Secret Key) which is approximately 259 bits possible or similarly is my MUK (Master Unlock Key), If they can succeed after that they can have access to everything i cherish in 1password data. which doesn't have to be related to AES 256 at all.
      Is this something that I understand correctly?

      1. The key benefit of Secret Key is that can add 128 bits of entropy to my Master Password.
        Because you all know that The user will create a Master Password that is not as strong as it should be.
        Therefore is controlled by the Secret Key to increase strength.
        Is this something that i understand correctly makes sense ?

      2. Secret key that is hidden on the user's device
        As I have seen in white paper: it is stored in a broswer that signs in. And keep in the desktop app. Right? You said that a skilled attacker could find it. Therefore, general users Will not be able to reveal the secret key clearly?
        Can you tell me what It is stored in the inner part of 1password desktop app?

  • Edit the question 1 a little for new understanding :

    I would like to know In the event that someone tries to access the item data stored in my 1password.
    They have only one way is must computational effort to bits of entropy for my key (key is Master Password + Secret Key) which is approximately 259 bits possible or similarly is my MUK (Master Unlock Key), If they can succeed after that they can have access to everything i cherish in 1password data. Which cannot be directly arbitrary compute AES256, Must always be compute via the key(Master Password + Secret Key) to decipher.
    Is this something that I understand correctly?

  • DanielPDanielP

    Team Member

    @sector:

    I would like to know In the event that someone tries to access the item data stored in my 1password.
    They have only one way is must computational effort to bits of entropy for my key (key is Master Password + Secret Key) which is approximately 259 bits possible or similarly is my MUK (Master Unlock Key), If they can succeed after that they can have access to everything i cherish in 1password data. Which cannot be directly arbitrary compute AES256, Must always be compute via the key(Master Password + Secret Key) to decipher.
    Is this something that I understand correctly?

    That's correct: the only way to decrypt your 1Password data is by having both the Master Password and the Secret Key.

    The key benefit of Secret Key is that can add 128 bits of entropy to my Master Password.
    Because you all know that The user will create a Master Password that is not as strong as it should be. Therefore is controlled by the Secret Key to increase strength. Is this something that i understand correctly makes sense ?

    This is true, but it's not just a matter of key strength: the Secret Key exists also to protect you against certain types of attack. Specifically, the Secret Key protects your data outside of your devices. The Master Password protects the data that is already stored on your device, while the Secret Key protects you against an attack against our servers. We never receive your Secret Key, so it protects you against this type of attack as well.

    So in summary, the Secret Key certainly helps make your encryption key stronger, but it's not the only benefit.

    Secret key that is hidden on the user's device
    As I have seen in white paper: it is stored in a broswer that signs in. And keep in the desktop app. Right? You said that a skilled attacker could find it. Therefore, general users Will not be able to reveal the secret key clearly? Can you tell me what It is stored in the inner part of 1password desktop app?

    You can reveal your Secret Key in the 1Password apps. For example, do to this in the 1Password for Mac app, you can go to 1Password Preferences > Accounts tab > Select your 1Password account, hover over the Secret Key field and select the reveal button. This is because the Secret Key is a secret to us, but you definitely know your Secret Key. So you are always able to show it on a device where you have logged into already.

    ===
    Daniel
    1Password Security Team

  • sectorsector
    edited May 23

    @DanielP, Thank you very much for your confirmation and further explanation.

    You can reveal your Secret Key in the 1Password apps.
    So you are always able to show it on a device where you have logged into already.

    Yes, it makes sense, I definitely understand this. I use 1password for windows.
    However, the process is similar: Choose Accounts and select my account> Select Secret Key field > and click the Copy button.
    Of course, i must unlock the 1Password app before accessing the Secret Key.

    I may ask the not exact question,
    Is there a way to access my Secret Key in my device without having to unlock 1password.
    For example: an attacker with expertise like this, or you can access my device or steal my device. Of course you don't know my Master Password to unlock the 1password app. But will you have a method to search only for my Secret Key?
    This is the case that I was really curious.

  • BenBen AWS Team

    Team Member

    It is possible to obtain the Secret Key from a device that has been authorized to your account without knowing the Master Password. An attacker would just need access to your device. Whole disk encryption (e.g. BitLocker) and locking your device when not in use can help prevent such issues.

    Ben

  • @Ben, Thank you for your confirmation and suggestions.
    I haved tried to read the section "Locally exposed Secret key" in Security Design White Paper.
    Therefore, according to my understanding,
    I can conclude that..
    The Secret Key is not designed to protect exposed itself in the device. Because the Secret Key must be used to derive the user's MUK it cannot be encrypted by the same MUK.

    I copied some text from Security Design White Paper.

    The Secret Key is stored on the local device unencrypted. Where possible, the Secret Key will be put into something provided by your system for storing authentication secrets. when 1Password has been used from a web browers, the Secret Key is stored in the browser's local data store, a fairly exposed location.

    Or in 1password for windows, meaning that it is hidden from the eyes of ordinary users like me to search. Because i can only see it from the 1password app, but for someone with expertise or your team can watch it easily, right?

  • DanielPDanielP

    Team Member
    edited May 25

    @sector:

    your team can watch it easily, right?

    Absolutely not. The 1Password Team cannot ever see your Secret Key, it's stored on your device. We cannot see what you have on your computer. This is exactly the point that I mentioned in my previous post: only you have access to the Secret Key.

    But because the Secret Key is stored on your device, a skilled attacker with access to your computer can find it. But they won't be able to do much with it because they would be missing the Master Password, which only you know and which is not stored anywhere (not even on your device).

    ===
    Daniel
    1Password Security Team

  • @DanielP,

    But because the Secret Key is stored on your device, a skilled attacker with access to your computer can find it. But they won't be able to do much with it because they would be missing the Master Password

    I began to understand this situation from what you described as that it must be a skilled attacker or only a 1Password team can find it, by having accessing, stealing, received my device. Because ordinary users or me have only one way to see the Secret Key on their device is in the 1password app only.

    Thank you very much, appreciate from the heart the explaining my question.

  • DanielPDanielP

    Team Member

    @sector:

    I began to understand this situation from what you described as that it must be a skilled attacker or only a 1Password team can find it, by having accessing, stealing, received my device.

    And just to clarify once again to avoid any misunderstanding, because this is an important security detail: we are talking about the case of a skilled attacker here, with access to your device. The 1Password Team never has access to this information.

    Because ordinary users or me have only one way to see the Secret Key on their device is in the 1password app only.

    That's correct.

    Thank you very much, appreciate from the heart the explaining my question.

    Anytime, please don't hesitate reaching out if you have any security questions :+1:

    ===
    Daniel
    1Password Security Team

  • @sector there's two more things you ought to be aware of:

    • The first 8 characters of the secret key are known to 1Password (this isn't a security issue)
    • Your secret key is sent to (Apple if Keychain is enabled) (Google if backups are enabled)

    There's no way to prevent your secret key from being sent to Apple (on iPhones) or Google (on Androids) if you have the respective features enabled. This isn't well-documented but you really should disable Keychain / Google Backups if a high level of security is required.

    • Apple currently use very good security to encrypt your secret key on Apple's servers
    • Google use variable security to encrypt your secret key on their servers depending upon the version of Android you're using

    Therefore the potential attack is somebody who can gain access to your Apple/Google credentials and cause a device to sync. This'll expose your secret key (but not your master password).

  • BenBen AWS Team

    Team Member

    @nickwaters

    That is a fair observation about the backups that happen to Apple/Google, however:

    Therefore the potential attack is somebody who can gain access to your Apple/Google credentials and cause a device to sync.

    The Secret Key alone is not enough to authorize a device. The Master Password is also required. 2FA would also be required if enabled.

    This'll expose your secret key (but not your master password).

    True. :)

    This isn't well-documented

    There is always room for improvement, however we do talk about this in our primary guide about the Secret Key:

    About your Secret Key

    "Encrypted copies of your Secret Key are stored in your device backups and keychains to provide data loss protection. If you have iCloud Drive enabled and lose your Mac, iPhone, or iPad, you can restore from a backup and unlock 1Password with just your Master Password. It’s the same for Android backups."

    Cheers. :)

    Ben

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