1AESPIPE(1) COMMANDS AESPIPE(1)
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6 aespipe - AES encrypting or decrypting pipe
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9 aespipe [options] <inputfile >outputfile
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12 aespipe reads from standard input and writes to standard output. It can
13 be used to create and restore encrypted tar or cpio archives. It can be
14 used to encrypt and decrypt loop-AES compatible encrypted disk images.
15 aespipe encrypts and decrypts blocks of data. If you are looking for
16 general purpose encrypting tool that preserves data size at byte granu‐
17 larity, then please take a look at GnuPG.
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19 The AES cipher is used in CBC (cipher block chaining) mode. Data is
20 encrypted and decrypted in 512 byte chains. aespipe supports three key
21 setup modes; single-key, multi-key-v2 and multi-key-v3 modes. Single-
22 key mode uses simple sector IV and one AES key to encrypt and decrypt
23 all data sectors. Multi-key-v2 mode uses cryptographically more secure
24 MD5 IV and 64 different AES keys to encrypt and decrypt data sectors.
25 In multi-key mode first key is used for first sector, second key for
26 second sector, and so on. Multi-key-v3 is same as multi-key-v2 except
27 is uses one extra 65th key as additional input to MD5 IV computation.
28 See -K option for more information about how to enable multi-key-v3
29 mode.
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31 Recommended key setup mode is multi-key-v3, which is based on gpg
32 encrypted key files. In this mode, the passphrase is protected against
33 optimized dictionary attacks via salting and key iteration of gpg.
34 Passphrase length should be 20 characters or more.
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36 Single-key mode preserves input size at 16 byte granularity. Multi-key
37 mode preserves input size at 512 byte granularity. If input size is not
38 multiple of 16 or 512 bytes, input data is padded with null bytes so
39 that both input and output sizes are multiples of 16 or 512 bytes.
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41 If "ulimit -l" is set to "unlimited" then aespipe attempts to lock its
42 RAM so that encryption keys do not leak to unencrypted swap. If "ulimit
43 -l" is something other than "unlimited" then aespipe will proceed with‐
44 out locked RAM.
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47 -A gpgAgentSocket
48 Read passphrase of gpg encrypted key file from gpg-agent instead
49 of the terminal. aespipe runs gpg to decrypt a key file, and gpg
50 talks to gpg-agent using gpgAgentSocket. Usually this data is in
51 GPG_AGENT_INFO environment variable. The environment that is
52 passed to gpg is very minimal. Normally gpg passes some envi‐
53 ronment variables to gpg-agent, but in this case, there aren't
54 any. For best results, you may want to configure gpg-agent so
55 that it "keeps" and uses its own environment. Defining "keep-
56 tty", "keep-display" and "pinentry-program" in $HOME/.gnupg/gpg-
57 agent.conf configuration file is a good start.
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59 -C itercountk
60 Runs hashed passphrase through itercountk thousand iterations of
61 AES-256 before using it for data encryption. This consumes lots
62 of CPU cycles at program start time but not thereafter. In com‐
63 bination with passphrase seed this slows down dictionary
64 attacks. Iteration is not done in multi-key mode.
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66 -d Decrypt data. If this option is not specified, default operation
67 is to encrypt data.
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69 -e encryption
70 Following encryption types are recognized: AES128 (default),
71 AES192 and AES256. Encryption type names are case insensitive.
72 AES128 defaults to using SHA-256 passphrase hash, AES192
73 defaults to using SHA-384 passphrase hash, and AES256 defaults
74 to using SHA-512 passphrase hash.
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76 -G gpghome
77 Set gpg home directory to gpghome, so that gpg uses public/pri‐
78 vate keys on gpghome directory. This is only used when gpgkey
79 file needs to be decrypted using public/private keys. If gpgkey
80 file is encrypted with symmetric cipher only, public/private
81 keys are not required and this option has no effect.
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83 -H phash
84 Uses phash function to hash passphrase. Available hash functions
85 are sha256, sha384, sha512 and rmd160. unhashed1 and unhashed2
86 functions also exist for compatibility with some obsolete imple‐
87 mentations. Hash type names are case insensitive.
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89 -K gpgkey
90 Passphrase is piped to gpg so that gpg can decrypt file gpgkey
91 which contains the real keys that are used to encrypt data. If
92 decryption requires public/private keys and gpghome is not spec‐
93 ified, all users use their own gpg public/private keys to
94 decrypt gpgkey. Decrypted gpgkey should contain 1 or 64 or 65
95 keys, each key at least 20 characters and separated by newline.
96 If decrypted gpgkey contains 64 or 65 keys, then aespipe is put
97 to multi-key mode. 65th key, if present, is used as additional
98 input to MD5 IV computation.
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100 -O sectornumber
101 Set IV offset in 512 byte units. Default is zero. Data is
102 encrypted in 512 byte CBC chains and each 512 byte chain starts
103 with IV whose computation depends on offset within the data.
104 This option can be used to start encryption or decryption in
105 middle of some existing encrypted disk image.
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107 -p fdnumber
108 Read the passphrase from file descriptor fdnumber instead of the
109 terminal. If -K option is not being used (no gpg key file), then
110 aespipe attempts to read 65 keys from passwdfd, each key at
111 least 20 characters and separated by newline. If aespipe suc‐
112 cessfully reads 64 or 65 keys, then aespipe is put to multi-key
113 mode. If aespipe encounters end-of-file before 64 keys are read,
114 then only first key is used in single-key mode.
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116 -P cleartextkey
117 Read the passphrase from file cleartextkey instead of the termi‐
118 nal. If -K option is not being used (no gpg key file), then
119 aespipe attempts to read 65 keys from cleartextkey, each key at
120 least 20 characters and separated by newline. If aespipe suc‐
121 cessfully reads 64 or 65 keys, then aespipe is put to multi-key
122 mode. If aespipe encounters end-of-file before 64 keys are read,
123 then only first key is used in single-key mode. If both -p and
124 -P options are used, then -p option takes precedence. These are
125 equivalent:
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127 aespipe -p3 -K foo.gpg -e AES128 ... 3<someFileName
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129 aespipe -P someFileName -K foo.gpg -e AES128 ...
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131 In first line of above example, in addition to normal open file
132 descriptors (0==stdin 1==stdout 2==stderr), shell opens the file
133 and passes open file descriptor to started aespipe program. In
134 second line of above example, aespipe opens the file itself.
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136 -q Be quiet and don't complain about write errors.
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138 -S pseed
139 Sets encryption passphrase seed pseed which is appended to user
140 supplied passphrase before hashing. Using different seeds makes
141 dictionary attacks slower but does not prevent them if user sup‐
142 plied passphrase is guessable. Seed is not used in multi-key
143 mode.
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145 -T Asks passphrase twice instead of just once.
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147 -v Verbose mode. Prints diagnostics to stderr about key length,
148 single/multi key mode, and selected code optimizations
149 (x86/amd64/padlock/intelaes).
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151 -w number
152 Wait number seconds before asking passphrase.
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155 aespipe returns 0 on success, nonzero on failure.
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158 Source is available from http://loop-aes.sourceforge.net/
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161 Jari Ruusu
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165LINUX February 23 2011 AESPIPE(1)