Extra information in public key
dsrbecky at gmail.com
Tue Aug 9 00:51:02 CEST 2005
I just found up-to-date RFC 2440:
Here is 5.12:
> 5.12. User Attribute Packet (Tag 17)
> The User Attribute packet is a variation of the User ID packet. It
> is capable of storing more types of data than the User ID packet
> which is limited to text. Like the User ID packet, a User Attribute
> packet may be certified by the key owner ("self-signed") or any
> other key owner who cares to certify it. Except as noted, a User
> Attribute packet may be used anywhere that a User ID packet may be
> While User Attribute packets are not a required part of the OpenPGP
> standard, implementations SHOULD provide at least enough
> compatibility to properly handle a certification signature on the
> User Attribute packet. A simple way to do this is by treating the
> User Attribute packet as a User ID packet with opaque contents, but
> an implementation may use any method desired.
> The User Attribute packet is made up of one or more attribute
> subpackets. Each subpacket consists of a subpacket header and a
> body. The header consists of:
> - the subpacket length (1, 2, or 5 octets)
> - the subpacket type (1 octet)
> and is followed by the subpacket specific data.
> The only currently defined subpacket type is 1, signifying an image.
> An implementation SHOULD ignore any subpacket of a type that it does
> not recognize. Subpacket types 100 through 110 are reserved for
> private or experimental use.
The important sentence is the last one: there are 11 types to play with.
I suggest to take pick one type between 100 and 110 and use it to store
extra information. Since we may want to add various data, I suggest to
store them as a series of named proprieties.
The attribute format could look like this:
- Magic number identifying this experimental attribute
- UTF-8 Name of property 1
- Data length for property 1
- Data of property 1
- UTF-8 Name of property 2
- Data length for property 2
- Data of property 2
And the content might look like this:
City=Usti nad Labem
Telephone=+65 536 1024
Prefers encrypted mail=true
Prefers signed mail=true
PGP key url=http://www.gnupg.org/dsrbecky/pgp.key
As this attribute will contain a lot of text, it should be encapsulated
in Compressed Data Packet (Tag 8).
So, what do you think?
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