Cryptsetup: Tutorial & Best Practices

Tool to encrypt block devices

Cryptsetup is a Linux utility that allows you to create, manage, and mount encrypted block devices or partitions. It is based on the dm-crypt kernel module, which provides a hardware-accelerated encryption layer for block devices.

To use cryptsetup, you will first need to create an encrypted block device or partition using one of the available encryption algorithms (such as AES or Twofish). This is done using the cryptsetup luksFormat command, which will prompt you for a passphrase that will be used to protect the data on the device.

Once the encrypted block device or partition has been created, you can use the cryptsetup open command to mount it. This will prompt you for the passphrase, and if it is correct, the encrypted device will be opened and mounted as a regular block device.

Cryptsetup supports a variety of encryption algorithms and options, and it can be used to create and manage encrypted devices on a wide range of Linux systems. It is a powerful and flexible tool for protecting data on block devices, and it is widely used in Linux to improve the security of data storage.

To use cryptsetup to create an encrypted file system on Linux, you will need to follow these steps:

Install cryptsetup: To install cryptsetup on a Debian-based system (such as Ubuntu), you can use the following command:
```
sudo apt-get update && sudo apt-get install cryptsetup
```
To install cryptsetup on a Red Hat-based system (such as CentOS), you can use the following command:
```
sudo yum install cryptsetup
```
Create a block device or partition: To create an encrypted file system with cryptsetup, you will need to create a block device or partition that will be used to store the data. You can do this using tools such as fdisk, parted, or gparted.

For example, to create a new partition on a disk using fdisk, you can use the following commands:
```
sudo fdisk /dev/sdb
# n (create a new partition)
# p (create a primary partition)
# 1 (use partition number 1)
# (accept default first sector)
# (accept default last sector)
# w (write the partition table and exit)
```
This will create a new partition on the /dev/sdb disk, and you can use it to store the encrypted data.
Create an encrypted block device: To create an encrypted block device, you can use the cryptsetup luksFormat command. This command will prompt you for a passphrase that will be used to protect the data on the device.

For example, to create an encrypted block device on the /dev/sdb1 partition using the AES-256-XTS encryption algorithm, you can use the following command:
```
sudo cryptsetup luksFormat /dev/sdb1 -c aes-xts-plain64 -s 512
```
This will create an encrypted block device on the /dev/sdb1 partition, and it will prompt you for a passphrase. You will need to enter the passphrase twice to confirm it.
Open the encrypted block device: Once the encrypted block device has been created, you can use the cryptsetup open command to mount it. This will prompt you for the passphrase, and if it is correct, the encrypted device will be opened and mounted as a regular block device.

For example, to open the encrypted block device and mount it on the /mnt/encrypted directory, you can use the following command:
```
sudo cryptsetup open /dev/sdb1 encrypted -d /dev/urandom
```
This will open the encrypted block device and mount it on the /mnt/encrypted directory. You will be able to access the data on the device as if it were a regular block device.
Create a file system: Once the encrypted block device has been mounted, you can create a file system on it using tools such as mkfs or mke2fs.

For example, to create an ext4 file system on the encrypted block device, you can use the following command:
```
sudo mkfs.ext4 /dev/mapper/encrypted
```
This will create an ext4 file system on the encrypted block device, and you will be able to store and access data on the device as if it were a regular file system.

Mount the file system:

mount /dev/mapper/encrypted /mnt/encrypted

Unmount the file system: To unmount the encrypted file system, you can use the umount command. For example, to unmount the /mnt/encrypted directory, you can use the following command:
```
sudo umount /mnt/encrypted
```
Close the crypt device To close the encrypted block device, you can use the cryptsetup close command.