When encrypting a user's home directory, either during the install procedure or later using ecryptfs-migrate-home, what encryption algorithm / key size is used by default?
ecryptfs algorithm is aes.
It can be shown during the creation of a new encrypted mount point of folder that only aes is presently loaded but
ecryptfs supports other logarithms.
bruno@ubuvbox:~$ sudo mount -t ecryptfs secret/ ~/secret/ Passphrase: Select cipher: 1) aes: blocksize = 16; min keysize = 16; max keysize = 32 (loaded) 2) blowfish: blocksize = 16; min keysize = 16; max keysize = 56 (not loaded) 3) des3_ede: blocksize = 8; min keysize = 24; max keysize = 24 (not loaded) 4) cast6: blocksize = 16; min keysize = 16; max keysize = 32 (not loaded) 5) cast5: blocksize = 8; min keysize = 5; max keysize = 16 (not loaded) Selection [aes]:
Default selected cipher is between
The above answer is right, that AES is the cipher, but the reasoning is wrong.
User's home directories are configured by the script ecryptfs-setup-private.
In that shell script, the cipher and key length are harcoded:
Likewise, in the C source code of the setuid mount helper, mount.ecryptfs_private, it is also hardcoded:
#define KEY_BYTES 16 #define KEY_CIPHER "aes"
These values were hard coded to minimize the support burden of helping millions of users encrypt their home directories.