aespipe(1)
NAME
aespipe - AES encrypting or decrypting pipe
SYNOPSIS
aespipe [options] <inputfile >outputfile
DESCRIPTION
aespipe reads from standard input and writes to standard output. It can be used to create and restore encrypted tar or cpio archives. It can be used to encrypt and decrypt loop-AES compatible encrypted disk images. aespipe encrypts and decrypts blocks of data. If you are looking for general purpose encrypting tool that preserves data size at byte granularity, then please take a look at GnuPG. The AES cipher is used in CBC (cipher block chaining) mode. Data is encrypted and decrypted in 512 byte chains. aespipe supports three key setup modes; single-key, multi-key-v2 and multi-key-v3 modes. Single- key mode uses simple sector IV and one AES key to encrypt and decrypt all data sectors. Multi-key-v2 mode uses cryptographically more secure MD5 IV and 64 different AES keys to encrypt and decrypt data sectors. In multi-key mode first key is used for first sector, second key for second sector, and so on. Multi-key-v3 is same as multi-key-v2 except is uses one extra 65th key as additional input to MD5 IV computation. See -K option for more information about how to enable multi-key-v3 mode. Recommended key setup mode is multi-key-v3, which is based on gpg encrypted key files. In this mode, the passphrase is protected against optimized dictionary attacks via salting and key iteration of gpg. Passphrase length should be 20 characters or more. Single-key mode preserves input size at 16 byte granularity. Multi-key mode preserves input size at 512 byte granularity. If input size is not multiple of 16 or 512 bytes, input data is padded with null bytes so that both input and output sizes are multiples of 16 or 512 bytes. If "ulimit -l" is set to "unlimited" then aespipe attempts to lock its RAM so that encryption keys do not leak to unencrypted swap. If "ulimit -l" is something other than "unlimited" then aespipe will proceed without locked RAM.
OPTIONS
-A gpgAgentSocket
Read passphrase of gpg encrypted key file from gpg-agent instead
of the terminal. aespipe runs gpg to decrypt a key file, and gpg
talks to gpg-agent using gpgAgentSocket. Usually this data is in
GPG_AGENT_INFO environment variable. The environment that is
passed to gpg is very minimal. Normally gpg passes some
environment variables to gpg-agent, but in this case, there
aren't any. For best results, you may want to configure gpg-
agent so that it "keeps" and uses its own environment. Defining
"keep-tty", "keep-display" and "pinentry-program" in
$HOME/.gnupg/gpg-agent.conf configuration file is a good start.
-C itercountk
Runs hashed passphrase through itercountk thousand iterations of
AES-256 before using it for data encryption. This consumes lots
of CPU cycles at program start time but not thereafter. In
combination with passphrase seed this slows down dictionary
attacks. Iteration is not done in multi-key mode.
-d Decrypt data. If this option is not specified, default operation
is to encrypt data.
-e encryption
Following encryption types are recognized: AES128 (default),
AES192 and AES256. Encryption type names are case insensitive.
AES128 defaults to using SHA-256 passphrase hash, AES192
defaults to using SHA-384 passphrase hash, and AES256 defaults
to using SHA-512 passphrase hash.
-G gpghome
Set gpg home directory to gpghome, so that gpg uses
public/private keys on gpghome directory. This is only used when
gpgkey file needs to be decrypted using public/private keys. If
gpgkey file is encrypted with symmetric cipher only,
public/private keys are not required and this option has no
effect.
-H phash
Uses phash function to hash passphrase. Available hash functions
are sha256, sha384, sha512 and rmd160. unhashed1 and unhashed2
functions also exist for compatibility with some obsolete
implementations. Hash type names are case insensitive.
-K gpgkey
Passphrase is piped to gpg so that gpg can decrypt file gpgkey
which contains the real keys that are used to encrypt data. If
decryption requires public/private keys and gpghome is not
specified, all users use their own gpg public/private keys to
decrypt gpgkey. Decrypted gpgkey should contain 1 or 64 or 65
keys, each key at least 20 characters and separated by newline.
If decrypted gpgkey contains 64 or 65 keys, then aespipe is put
to multi-key mode. 65th key, if present, is used as additional
input to MD5 IV computation.
-O sectornumber
Set IV offset in 512 byte units. Default is zero. Data is
encrypted in 512 byte CBC chains and each 512 byte chain starts
with IV whose computation depends on offset within the data.
This option can be used to start encryption or decryption in
middle of some existing encrypted disk image.
-p fdnumber
Read the passphrase from file descriptor fdnumber instead of the
terminal. If -K option is not being used (no gpg key file), then
aespipe attempts to read 65 keys from passwdfd, each key at
least 20 characters and separated by newline. If aespipe
successfully reads 64 or 65 keys, then aespipe is put to multi-
key mode. If aespipe encounters end-of-file before 64 keys are
read, then only first key is used in single-key mode.
-P cleartextkey
Read the passphrase from file cleartextkey instead of the
terminal. If -K option is not being used (no gpg key file), then
aespipe attempts to read 65 keys from cleartextkey, each key at
least 20 characters and separated by newline. If aespipe
successfully reads 64 or 65 keys, then aespipe is put to multi-
key mode. If aespipe encounters end-of-file before 64 keys are
read, then only first key is used in single-key mode. If both -p
and -P options are used, then -p option takes precedence. These
are equivalent:
aespipe -p3 -K foo.gpg -e AES128 ... 3<someFileName
aespipe -P someFileName -K foo.gpg -e AES128 ...
In first line of above example, in addition to normal open file
descriptors (0==stdin 1==stdout 2==stderr), shell opens the file
and passes open file descriptor to started aespipe program. In
second line of above example, aespipe opens the file itself.
-q Be quiet and don't complain about write errors.
-S pseed
Sets encryption passphrase seed pseed which is appended to user
supplied passphrase before hashing. Using different seeds makes
dictionary attacks slower but does not prevent them if user
supplied passphrase is guessable. Seed is not used in multi-key
mode.
-T Asks passphrase twice instead of just once.
-v Verbose mode. Prints diagnostics to stderr about key length,
single/multi key mode, and selected code optimizations
(x86/amd64/padlock/intelaes).
-w number
Wait number seconds before asking passphrase.
RETURN VALUE
aespipe returns 0 on success, nonzero on failure.
AVAILABILITY
Source is available from http://loop-aes.sourceforge.net/
AUTHORS
Jari Ruusu
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