Use A Uuid To Generate Encryption Key

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  1. Use A Uuid To Generate Encryption Key Iphone
  2. Generate Uuid Linux

After you have retrieved the X.509 certificate and used its public key to encrypt your content key, create a ContentKey entity and set its property values accordingly. One of the values that you must set when create the content key is the type. When using storage encryption, the value should be set to '1'. Generate UUID Thanks for using this software, for Cofee/Beer/Amazon bill and further development of this project please Share. Any private key value that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen, for extra security run this software on your network. There are multiple ways of generating an encryption key. Most implementations rely on a random object. All examples mentioned here use a secure cryptographic randomizer. If you are using Foreign Keys, and they are also UUID's, that's another 1MB of storage for each Foreign Key. UUIDs degrade database performance. If you use a UUID as an identifier for a table, you're going to have to index it. Unfortunately, UUID's don't index well. The problem is their size and randomness. Apr 23, 2019 Note also that most databases WILL create a unique id as the primary key for every record in a table–though the value is only unique to that table. Some can be told to create a uuid for that primary key, for what that’s worth. Then if you are going to pass such an id on a URL, you should use the urlencodedformat function around that.

The architectural consequences of using UUID/GUID's may outweigh their benefits.

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Stumbling my way through the great wastelands of enterprise software development.

For the purpose of this post, I will use UUID (Universally Unique Identifier) to mean both UUID and GUID (Globally Unique Identifier, Microsoft's implementation of UUID).

I've been thinking a lot about UUID's lately. The system I've inherited at work is plagued by their usage. To many developers, the UUID seems like a totally awesome way to establish the identity of a record in a system. I mean, how cool is it that you can generate an ID unique to every system in the world?.

The purpose of this post is to discuss appropriate and inappropriate uses of UUIDs. My goal is to encourage engineers to think about the general consequences of data type selection for identifiers in their architectures.

To most databases, UUID's are just 36 character strings.

Databases like MySQL do not have a native implementation of the data structure. This means the column that carries the value must at least be 36 characters (VARCHAR(36)). When you consider the text encoding (e.g. MySQL character set) used to represent strings, this could mean 2-3 bytes per character (if using UTF-8). That means at least 72 bytes per identifier!

While this doesn't seem like a big deal, consider that for every 13,889 identifiers, your database will consume 1MB of storage. If you are using Foreign Keys, and they are also UUID's, that's another 1MB of storage for each Foreign Key.

UUIDs degrade database performance.

If you use a UUID as an identifier for a table, you're going to have to index it. Unfortunately, UUID's don't index well. The problem is their size and randomness. Indexes are trees that grow and branch as you add more data. Sequential values tend to index well because they don't require large sections of the index to be realigned (e.g. splitting a value into a new branch of values - refer to B-tree). UUID's are designed to be non-sequential and they are very large compared to an integer. This means the more UUIDs you insert, the larger the insertion penalty will be.

Don't take my word for it, just look at the statistics: http://kccoder.com/mysql/uuid-vs-int-insert-performance/. Notice the nearly consistent insertion time of a long integer vs. the UUID. More importantly, note that the scale on the left is 'insert time in hours'.

You will very certainly see better performance on queries using integers as well, though this might not be as pronounced. Auto incremented integers will almost always be smaller, meaning scans against tables/records will be more efficient. On the other hand, the index that stores UUID identifiers will grow much larger and at a faster rate than integers. This means a UUID index will become disk bound (because it can't fit completely into memory) more quickly than an integer index.

Are UUID's the right data structure for the task?

The point of a UUID is to have a universally unique identifier. There's generally two reason to use UUIDs:

  1. You do not want a database (or some other authority) to centrally control the identity of records.
  2. There's a chance that multiple components may independently generate a non-unique identifier.

These concerns should generally only arise when you are in a concurrent or distributed environment. The first reason is about avoiding an unnecessary call to an external system. You don't want a high-throughput message broker like RabbitMQ asking MySQL for an identifier every time it publishes a message. The second is generally a concern of a distributed system that requires a high write throughput and uses the key (generally a UUID) to determine the instance/server/partition it needs to write to.

The question is, does your system actually have the same requirements?

The following are use cases in which I'd argue you don't need a UUID.

1. Application writes records to a single database (or a cluster in master/slave configuration).

If there is only one database accepting writes, you don't have a need to route records using a unique key.

If portions of the data structure are going to update more than one table (and you need the ID before inserting records into those other tables in one single transaction), you could encapsulate the mutations in a stored procedure. I will admit that this may not be true in a NoSQL database with limited macro/remote execution functionality. In that case it may make sense to generate the ID outside of the database an perform simultaneous mutations. If you do this you are probably not doing it within a transaction and will need to account for inconsistency in your data stores if the operation fails mid-update.

2. There's a Natural Key for your record.

A natural key is a property or group of properties that make your record unique. A phone number or social security number could serve as a unique identifier. In a distributed system, this could be the combination of server IP, application, and timestamp. The point is, there may not be a need to have a UUID to establish record identity in a database. /generate-bitcoin-private-key-based-on-secret-exponet.html.

If you need to distribute writes across servers, you could simply hash the natural key (concatenating fields if it's a composite) for a unique identifier. If the hashing strategy is well know amongst components in the architecture, you will not need to store the hash (since components will know how to regenerate it on the fly when performing lookups).

3. When you need to present an ID to a user.

Consider an HR application for a small company (30 employees). Does a UUID make sense for an employee ID? Could you imagine if your employee number was: 2a6db8e1-8967-4511-9839-a7cb3a895710? Of course not! We're accustomed to a more friendly number we can remember.

There's an argument for this same kind of recognizability in the URI's we present users and application developers:

I can probably readily remember the second URL if that user identifier was mine. The first one? Forget it!

Conclusion

UUID's should be a last resort tactic,employed only after you have exhausted other strategies for determining uniqueness in an architecture. In a database, they are generally considered an anti-pattern and should be avoided due to the performance limitations in indexing their values. UUID's also not particularly friendly to users. Instead, engineers should use natural keys as much as possible, and auto incremented integers as an alternative (when it makes sense).

Stumbling my way through the great wastelands of enterprise software development.

These advanced steps are for system administrators and others who are familiar with the command line.

Create a FileVault master keychain

  1. Open the Terminal app on your Mac, then enter this command:
  2. When prompted, enter the master password for the new keychain, then enter it again when prompted to retype. Terminal doesn't show the password as you type.
  3. A key pair is generated, and a file named FileVaultMaster.keychain is saved to your desktop. Copy this file to a secure location, such an encrypted disk image on an external drive. This secure copy is the private recovery key that can unlock the startup disk of any Mac set up to use the FileVault master keychain. It is not for distribution.

In the next section, you will update the FileVaultMaster.keychain file that is still on your desktop. You can then deploy that keychain to Mac computers in your institution.

Remove the private key from the master keychain

After creating the FileVault master keychain, follow these steps to prepare a copy of it for deployment:

  1. Double-click the FileVaultMaster.keychain file on your desktop. The Keychain Access app opens.
  2. In the Keychain Access sidebar, select FileVaultMaster. If you see more than two items listed on the right, select another keychain in the sidebar, then select FileVaultMaster again to refresh the list.
  3. If the FileVaultMaster keychain is locked, click in the upper-left corner of Keychain Access, then enter the master password you created.
  4. From the two items shown on the right, select the one identified as ”private key” in the Kind column:
  5. Delete the private key: Choose Edit > Delete from the menu bar, enter the keychain master password, then click Delete when asked to confirm.
  6. Quit Keychain Access.

Now that the master keychain on your desktop no longer contains the private key, it's ready for deployment.

Deploy the updated master keychain on each Mac

After removing the private key from the keychain, follow these steps on each Mac that you want to be able to unlock with your private key.

  1. Put a copy of the updated FileVaultMaster.keychain file in the /Library/Keychains/ folder.
  2. Open the Terminal app and enter both of the following commands. These commands make sure that the file's permissions are set to -rw-r--r-- and the file is owned by root and assigned to the group named wheel.
  3. If FileVault is already turned on, enter this command in Terminal:
  4. If FileVault is turned off, open Security & Privacy preferences and turn on FileVault. You should see a message that a recovery key has been set by your company, school, or institution. Click Continue.

This completes the process. If a user forgets their macOS user account password and can't log in to their Mac, you can use the private key to unlock their disk.

Use the private key to unlock a user's startup disk

If a user forgot their account password and can't log in to their Mac, you can use the private recovery key to unlock their startup disk and access its FileVault-encrypted data.

  1. On the client Mac, start up from macOS Recovery by holding Command-R during startup.
  2. If you don't know the name (such as Macintosh HD) and format of the startup disk, open Disk Utility from the macOS Utilities window, then check the information Disk Utility shows for that volume on the right. If you see ”CoreStorage Logical Volume Group” instead of ”APFS Volume” or ”Mac OS Extended,” the format is Mac OS Extended. You will need this information in a later step. Quit Disk Utility when done.
  3. Connect the external drive that contains the private recovery key.
  4. From the menu bar in macOS Recovery, choose Utilities > Terminal.
  5. If you stored the private recovery key in an encrypted disk image, use the following command in Terminal to mount that image. Replace /path with the path to the disk image, including the .dmg filename extension:
    Example for a disk image named PrivateKey.dmg on a volume named ThumbDrive:
    hdiutil attach /Volumes/ThumbDrive/PrivateKey.dmg
  6. Use the following command to unlock the FileVault master keychain. Replace /path with the path to FileVaultMaster.keychain on the external drive. In this step and all remaining steps, if the keychain is stored in an encrypted disk image, remember to include the name of that image in the path.
    Example for a volume named ThumbDrive:
    security unlock-keychain /Volumes/ThumbDrive/FileVaultMaster.keychain
  7. Enter the master password to unlock the startup disk. If the password is accepted, the command prompt returns.

Continue as described below, based on how the user's startup disk is formatted.

APFS

If the startup disk is formatted for APFS, complete these additional steps:

  1. Enter the following command to unlock the encrypted startup disk. Replace 'name' with the name of the startup volume, and replace /path with the path to FileVaultMaster.keychain on the external drive or disk image:
    Example for a startup volume named Macintosh HD and a recovery-key volume named ThumbDrive:
    diskutil ap unlockVolume 'Macintosh HD' -recoveryKeychain /Volumes/ThumbDrive/FileVaultMaster.keychain
  2. Enter the master password to unlock the keychain and mount the startup disk.
  3. Use command-line tools such as ditto to back up the data on the disk, or quit Terminal and use Disk Utility.

Mac OS Extended (HFS Plus)

Use A Uuid To Generate Encryption Key Iphone

If the startup disk is formatted for Mac OS Extended, complete these additional steps:

Generate Uuid Linux

  1. Enter this command to get a list of drives and CoreStorage volumes:
  2. Select the UUID that appears after “Logical Volume,” then copy it for use in a later step.
    Example: +-> Logical Volume 2F227AED-1398-42F8-804D-882199ABA66B
  3. Use the following command to unlock the encrypted startup disk. Replace UUID with the UUID you copied in the previous step, and replace /path with the path to FileVaultMaster.keychain on the external drive or disk image:
    Example for a recovery-key volume named ThumbDrive:
    diskutil cs unlockVolume 2F227AED-1398-42F8-804D-882199ABA66B -recoveryKeychain /Volumes/ThumbDrive/FileVaultMaster.keychain
  4. Enter the master password to unlock the keychain and mount the startup disk.
  5. Use command-line tools such as ditto to back up the data on the disk. Or quit Terminal and use Disk Utility. Or use the following command to decrypt the unlocked disk and start up from it.
    Example for a recovery-key volume named ThumbDrive:
    diskutil cs decryptVolume 2F227AED-1398-42F8-804D-882199ABA66B -recoveryKeychain /Volumes/ThumbDrive/FileVaultMaster.keychain