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man/Makefile.in
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@@ -1,4 +1,4 @@
# Makefile.in generated by automake 1.12.4 from Makefile.am.
# Makefile.in generated by automake 1.12.6 from Makefile.am.
# @configure_input@
# Copyright (C) 1994-2012 Free Software Foundation, Inc.

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man/details.pod
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@@ -35,42 +35,119 @@ There are 2 modes of encryption available in pcp1:
=item B<Standard public key encryption>
In this mode, which is the default, a public key as specified
with B<-i> and a dynamically generated secret key will be used
for encryption. The public part of the generated sender key
will be included with the encrypted file, which the recipient
can use to decrypt it.
with B<-i> or B<-r> and your primary secret key will be used
for encryption.
Example command:
pcp1 -e -i 0x2BD734B15CE2722D -I message.txt -O cipher.z85
pcp1 -e -i 0x2BD734B15CE2722D -I message.txt -O message.asc
Here we didn't specify a recipient. Therefore the public
key given with -i will be used directly.
Another example:
pcp1 -e -r Bobby -r McCoy -I message.txt -O message.asc
=item B<Self encryption mode>
Pretty Curved Privacy doesn't provide symetric file encryption.
However there are cases when you need to encrypt a file just
for yourself. In such a case the file will be encrypted using
the public key part of your primary secret key and the secret
key itself (thanks to the wonders of ECC this works like a charm).
The file can be decrypted using the primary key pair.
You can also encrypt a file symetrically. No public key material
will be used in this mode.
While this works, the security of it totally depends on the
strength of your password, especially if the primary secret
used for this kind of encryption is stored in a vault on the
same system.
strength of the passphrase used for encryption.
Example command:
pcp1 -e -I message.txt -O cipher.z85
As you can see we didn't specify -i or -r and therefore pcp1
tries to use the primary keypair for encryption.
operates in self mode for encryption. It will ask you for a passphrase
to protect the encryption key.
=back
=head1 SIGNATURES
There are 3 modes for digital signatures available on pcp1:
=over
=item B<Standard NACL binary signatures>
In this mode, which is the default, an ED25519 signature will
be calculated from a BLAKE2 hash of the input file content. Both
the original file content plus the signature will be written to
the output file.
Example:
pcp1 -g -I message.txt -O message.asc -g
You will be asked for the passphrase to access your primary
secret key. The output file will be a binary file.
=item B<Armored NACL signatures>
While this mode does the very same calculations, the output
slightly differs. The output file will be marked as a signature
file, the signature itself will be appended with its own headers
and Z85 encoded.
Example:
pcp1 -g -I message.txt -O message.asc -g -z
You will be asked for the passphrase to access your primary
secret key. The output file will be a text file.
=item B<Detached NACL signatures>
In some cases you will need to have the signature separated
from the original input file, e.g. to sign download files. You
can generate detached signatures for such purposes. Still, the
signature will be calculated the same way as in standard signatures
but put out into a separate file. A detached signature file will always
be Z85 encoded.
Example:
pcp1 -g -I message.txt -O message.asc -g --detach
=back
=head1 SIGNED ENCRYPTION
Beside pure encryption and signatures pcp1 also supports signed
encryption. In this mode an input file will be encrypted and
a signature using your primary secret key from a BLAKE2 hash of
the file contents will be appended to it.
Example:
pcp1 -e -g -r Bobby -I README.txt -O README.asc
Please note the additional B<-g> parameter. The recipient can
decrypt and verify the so created data like this:
pcp1 -d -c -I README.asc -o README.txt
Please note the additional B<-c> parameter.
If decryption works, the output file will be written. If signature
verification fails you will be informed, but the decrypted
output will be left untouched. It is up to you how to react
on an invalid signature.
B<Caution: as of this writing (pcp version 0.2.0) there is
no offset marker included into the output which separates
the signature from the cipher. Therefore a recipient has to
know that the file is encrypted AND signed. If, for example,
the recpient leaves the -c parameter on such a file, the decryption
process will fail. Otherwise, if the user supplies -c on an
encrypted file without a signature, decryption will fail as well.>
Note: this behavior might change in the future.
=head1 VULNERABILITIES
@@ -217,95 +294,119 @@ Generate a random seed (32 bytes).
=item *
Generate a ED25519 keypair from that seed.
Generate a ED25519 sigining keypair from that seed.
=item *
Take the first 32 bytes of the generated ED25519 secret
and generate a SHA512 hash from it.
Generate a random seed (32 bytes).
=item *
Clamp bytes 0 and 31 which turns it into a Curve25519 secret.
=item *
Do scalar multiplication from that secret to retrieve
the matching public key.
Generate a Curve25519 encryption keypair from that seed.
=back
Take a look at the function B<pcp_keypairs()> for details.
So, while both secrets are stored in the sam PCP key, they
are otherwise unrelated. If one of them leaks, the other
cannot be recalculated from it.
Take a look at the function B<pcp_keypairs()> for details.
=head2 ENCRYPTED OUTPUT FORMAT
Encrypted output will always be Z85 encoded and has the following
format:
Encrypted output will always written as binary files. No armoring
supported yet. The encryption process works as this:
=over
=item generate a random symetric 32 byte key B<S>
=item encrypt it asymetrically for each recipient using a unique nonce (B<R>)
=item encrypt the input file 32k blockwise using the symetric key
=back
Symetric encryption works the very same with the recipient stuff
left out.
Formal format description, asymetric encrypted files:
+---------------------------------------------------------+
| Field Size Description |
+-------------+--------+----------------------------------+
| Pubkey | 32 | Publix key of the sender |
| Type | 1 | Filetype, 5=ASYM, 23=SYM |
+-------------|--------|----------------------------------+
| Nonce | 24 | Random Nonce |
| Len R | 4 | Number of recipients (*) |
+-------------|--------|----------------------------------+
| Recipients | R*72 | C(recipient)|C(recipient)... (*) |
+-------------|--------|----------------------------------+
| Encrypted | ~ | The actual encrypted data |
+-------------|--------|----------------------------------+
=head2 SIGNATURE FORMAT
Left out when doing symetric encryption.
Signatures will always be Z85 encoded and have the following
format:
Recipient field format:
+---------------------------------------------------------+
| Field Size Description |
+-------------+--------+----------------------------------+
| Key ID | 17 | Signers key id
| Nonce | 24 | Random Nonce, one per R |
+-------------|--------|----------------------------------+
| Ctime | 4 | Creation time, sec since epoch |
| Cipher | 48 | S encrypted with PK or R |
+-------------|--------|----------------------------------+
| Version | 4 | Signature version |
R is calculated using public key encryption using the senders
secret key, the recipients public key and a random nonce.
=head2 SIGNATURE FORMAT
There are different signature formats. Standard binary NACL
signatures have the following format:
+---------------------------------------------------------+
| Field Size Description |
+-------------+--------+----------------------------------+
| Content | ~ | Original file content |
+-------------|--------|----------------------------------+
| Signature | 96 | ED25519 signature of SHA256 Hash |
| \nnacl- | 6 | Offset separator |
+-------------|--------|----------------------------------+
| Hash | 64 | BLAKE2 hash of the content |
+-------------|--------|----------------------------------+
| Signature | 64 | ED25519 signature of BLAKE2 Hash |
+-------------|--------|----------------------------------+
The actual signature is not a signature over the whole content
of an input file but of a SHA256 hash of the content.
of an input file but of a BLAKE2 hash of the content.
Armored signatures have the following format:
----- BEGIN ED25519 SIGNED MESSAGE -----
Hash: Blake2
MESSAGE
----- BEGIN ED25519 SIGNATURE -----
Version: PCP v0.2.0
195j%-^/G[cVo4dSk7hU@D>NT-1rBJ]VbJ678H4I!%@-)bzi>zOba5$KSgz7b@R]A0!kL$m
MTQ-1DW(e1mma(<jH=QGA(VudgAMXaKF5AGo65Zx7-5fuMZt&:6IL:n2N{KMto*KQ$:J+]d
dp1{3}Ju*M&+Vk7=:a=J0}B
------ END ED25519 SIGNATURE ------
The Z85 encoded signature at the end contains the same signature
contents as the binary signature outlined above (hash+sig).
=head2 SIGNED ENCRYPTION FORMAT
Signed encrypted files are in binary form only. The first part is
the standard encrypted file as described in B<ENCRYPTED OUTPUT FORMAT>
followed by the binary signature described in B<SIGNATURE FORMAT> without
the offset separator.
=head2 Z85 ENCODING
B<pcp1> uses Z85 to encode exported keys and encrypted messages.
Therefore it includes a Z85 utility mode:
B<pcp1> can be used to encode and decode strings to Z85 encoding.
The option B<-z> encodes B<to> Z85, the option B<-Z> does the opposite
and decodes B<from> Z85.
If no input file have been specified using B<-I>, B<pcp1> expects the
input to come from B<STDIN>, otherwise it reads the contents
of B<file>.
Encoded or decoded output will be written to B<STDOUT> unless an
output file has been specified using the option B<-O>.
=head3 Z85 EXAMPLES
To encode a given file to Z85 and write the output to another:
pcp1 -z myfile.bin > myfile.z85
To decode the file created above and restore the original:
pcp1 -Z -d myfile.z85 > myfile.bin
To encode something from stdin to Z85:
ps axuw | pcp1 -z > pslist.z85
To decode the above and print to stdout:
pcp1 -Z -d pslist.z85
B<pcp1> uses Z85 to encode exported keys and armored signatures.
=head3 Z85 BACKGROUND
@@ -344,3 +445,9 @@ B<Trying to use another tool to decode an Z85 encoded string produced
by z85, might not work therefore, unless the tool takes the padding scheme
outlined above into account>.
=head2 PBP COMPATIBILITY
PCP tries to be fully compatible with PBP (https://github.com/stef/pbp). Encrypted
files and signatures - at least their binary versions - should be exchangable. However,
this is a work in progress and might not work under all circumstances. Also there's currently
no shared key format between pbp and pcp.