aespipe

AESPIPE(1)                         COMMANDS                         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



LINUX                          February 23 2011                     AESPIPE(1)