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107 lines
3.2 KiB
Plaintext
107 lines
3.2 KiB
Plaintext
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=head1 PCP1 KEYS
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B<pcp1> keys are stored in a binary file, called B<the vault>.
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It's by default located in B<~/.pcpvault> but you can of course
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specify another location using the B<-V> option.
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There are two kinds of keys: secret and public keys. In reality
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a secret key always includes its public key. Both types of keys
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can be exported to files and transfered to other people who can
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then import them. You should usually only do this with public keys
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though.
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There is a primary secret key which will always used for operations
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when no keyid has been specified. However, you may have as many
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secret keys in your vault as you like.
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Each key can be identified using its B<keyid> which looks like this:
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0xD49119E85266509F
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A public key exported from a secret key will have the same keyid
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as the secret key. When using for encryption, the keyid will be
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added to the message so that the receiver knows who was the
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sender of the message (B<This might change in the future. As of
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this writing I'm not sure if this was a good idea>).
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If you just want to know details about a key or the vault, use the
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B<-t> option.
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=head1 INTERNALS
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FIXME.
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=head1 Z85 ENCODING
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B<pcp1> uses Z85 to encode exported keys and encrypted messages.
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Therefore it includes a Z85 utility mode:
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B<pcp1> can be used to encode and decode strings to Z85 encoding.
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The option B<-z> encodes B<to> Z85, the option B<-Z> does the opposite
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and decodes B<from> Z85.
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If no input file have been specified using B<-I>, B<pcp1> expects the
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input to come from B<STDIN>, otherwise it reads the contents
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of B<file>.
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Encoded or decoded output will be written to B<STDOUT> unless an
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output file has been specified using the option B<-O>.
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=head2 EXAMPLES
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To encode a given file to Z85 and write the output to another:
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pcp1 -z myfile.bin > myfile.z85
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To decode the file created above and restore the original:
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pcp1 -Z -d myfile.z85 > myfile.bin
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To encode something from stdin to Z85:
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ps axuw | pcp1 -z > pslist.z85
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To decode the above and print to stdout:
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pcp1 -Z -d pslist.z85
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=head2 BACKGROUND
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The Z85 encoding format is described here: B<http://rfc.zeromq.org/spec:32>.
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It's part of ZeroMQ (B<http://zeromq.org>). Z85 is based on ASCII85 with
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a couple of modifications (portability, readability etc).
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To fulfil the requirements of the ZeroMQ Z85 functions, B<pcp1>
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does some additional preparations of raw input before actually doing the
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encoding, since the input for zmq_z85_encode() must be divisible by 4:
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Expand the input so that the resulting size is divisible by 4.
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Fill the added bytes with zeroes.
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Prepend the input with a one byte value which holds the number of zeroes
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added in the previous step.
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Example:
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Raw input:
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hello\0
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Here, the input size is 6, which is insufficient, therefore it has to be expanded
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to be 8. After the process the input looks like this:
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1hello\0\0
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So, we padded the input with 1 zero (makes 7 bytes) and preprended it with the
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value 1 (the number of zeros added): makes 8 bytes total.
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After decoding Z85 input the process will be reversed.
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B<Trying to use another tool to decode an Z85 encoded string produced
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by z85, might not work therefore, unless the tool takes the padding scheme
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outlined above into account>.
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