aespipe






aespipe − AES encrypting or decrypting pipe

aespipe [options] <inputfile >outputfile

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.



−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









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     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









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     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.









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aespipe returns 0 on success, nonzero on failure.

Source is available from http://loop‐aes.sourceforge.net/

Jari Ruusu