MAN page from PLD aespipe-2.2e-1.athlon.rpm

AESPIPE

Section: COMMANDS (1)
Updated: August 21 2004
Index

NAME

aespipe - AES encrypting or decrypting pipe

SYNOPSIS

aespipe[options] <inputfile >outputfile

DESCRIPTION

aespipereads from standard input and writes to standard output. It can be used tocreate and restore encrypted tar or cpio archives. It can be used to encryptand decrypt loop-AES compatible encrypted disk images.

The AES cipher is used in CBC (cipher block chaining) mode. Data isencrypted and decrypted in 512 byte chains.aespipesupports two key setup modes; single-key mode and multi-key mode. Single-keymode uses simple sector IV and one AES key to encrypt and decrypt all datasectors. Multi-key mode uses cryptographically more secure MD5 IV and 64different AES keys to encrypt and decrypt data sectors. In multi-key modefirst key is used for first sector, second key for second sector, and so on.See -K option for more information about how to enable multi-key mode.

Single-key mode preserves input size at 16 byte granularity. Multi-key modepreserves input size at 512 byte granularity. If input size is not multipleof 16 or 512 bytes, input data is padded with null bytes so that both inputand output sizes are multiples of 16 or 512 bytes.

Password string has a minimum length of 20 characters (or 1 character whenusing rmd160 password hash). Optional password seed (salt) and key iterationcount can be used to slow down dictionary attacks. Password seed is appendedto user supplied password before password is hashed using one way hash. Ifpassword iteration count is specified, password hash output is encrypted Nthousand times using AES-256. Unique seed prevents an adversary fromprecomputing hashes of passwords in his dictionary in advance, and thusmaking an optimized attack slower. Large password iteration count makesdictionary attack painfully slow.

OPTIONS

-C itercountk: Runs hashed password through itercountk thousand iterations of AES-256before using it for data encryption. This consumes lots of CPU cycles atprogram start time but not thereafter. In combination with password seedthis slows down dictionary attacks. Iteration is not done in multi-key mode.
-d: Decrypt data. If this option is not specified, default operation is toencrypt data.
-e encryption: Following encryption types are recognized: AES128 (default), AES192and AES256. Encryption type names are case insensitive. AES128 defaults tousing SHA-256 password hash, AES192 defaults to using SHA-384 password hash,and AES256 defaults to using SHA-512 password hash.
-G gpghome: Set gpg home directory to gpghome, so that gpg uses public/privatekeys on gpghome directory. This is only used when gpgkey file needs tobe decrypted using public/private keys. If gpgkey file is encrypted withsymmetric cipher only, public/private keys are not required and this optionhas no effect.
-H phash: Uses phash function to hash password. Available hash functions aresha256, sha384, sha512 and rmd160. Hash type names are case insensitive.
-K gpgkey: Password is piped to gpg so that gpg can decrypt file gpgkey whichcontains the real keys that are used to encrypt data. If decryption requirespublic/private keys and gpghome is not specified, all users use their owngpg public/private keys to decrypt gpgkey. Decrypted gpgkeyshould contain either 1 or 64 keys, each key at least 20 characters andseparated by newline. If decrypted gpgkey contains 64 keys, thenaespipe is put to multi-key mode.
-O sectornumber: Set IV offset in 512 byte units. Default is zero. Data is encrypted in 512byte CBC chains and each 512 byte chain starts with unique IV. This optioncan be used to start encryption or decryption in middle of some existingencrypted disk image.
-p fdnumber: Read the password from file descriptor fdnumber instead of theterminal. If -K option is not being used (no gpg key file), then aespipeattempts to read 64 keys from passwdfd, each key at least 20characters and separated by newline. If aespipe successfully reads 64 keys,then aespipe is put to multi-key mode. If aespipe encounters end-of-filebefore 64 keys are read, then only first key is used in single-key mode.
-q: Be quiet and don't complain about write errors.
-S pseed: Sets encryption password seed pseed which is appended to user suppliedpassword before hashing. Using different seeds makes dictionary attacksslower but does not prevent them if user supplied password is guessable.Seed is not used in multi-key mode.
-T: Asks password twice instead of just once.
-w number: Wait number seconds before asking password.

RETURN VALUE

aespipereturns 0 on success, nonzero on failure.

AVAILABILITY

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

AUTHORS

Jari Ruusu

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