PISP: Proposed solution for selective information sharing.

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cannon-c
Posts: 7
Joined: Wed Jan 25, 2017 10:05 am
os: linux

PISP: Proposed solution for selective information sharing.

Post by cannon-c » Wed Jan 25, 2017 10:15 am

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Title: Private Information Sharing Protocol [P.I.S.P.]
 Draft Version 1.1
  Author: Cannon Ciota <cannon@cannon-ciota.info> Created: 2017-01-21

 Abstract
	Opt in method of using publicly accessible directories,
	particularly namecoin, to list updatable information which
	can only be viewed by authorized entities.

 Motivation
	Primarily intended as a usecase for (but not limited to)
	namecoin as a proposal for a standard allowing entries such
	as contact information i.e. phone numbers, addresses, etc. to
	be listed in a way that allows only authorized entities of the
	entry owner's choice to be able to interpret such information.
	Namecoin, a secure decentralized universal directory, is
	great for binding a multitude of information to a single human
	readable identity in such a way that is not only censorship
	resistant, resilient, and verifiable, but also immune from
	tampering. However, due to the public nature of blockchain,
	what namecoin currently lacks in is a standard way to list
	specific portions of an identity's datastore in a way which
	allows sharing of such information to authorized entities only,
	at the control and discretion of the identity owner.

  Specification
	Each namecoin identity would have listed a public key, or
	pointer to a public key of which the owner's namecoin client
	software has a corresponding private key. This public/private
	keypair would be used for this Private Information Sharing
	Protocol, or P.I.S.P for short.  The public key would be
	denoted in the standard namecoin JSON format using one of two
	forms, embedded or as a pointer. A pointer would be useful
	in scenarios in which a large key is used or if space within
	the namecoin identity's limited size for data is scarce.

Examples

Embedded: 
- ---------
 {
   "pisp-pub":"026D3CA82768BC8D8E512EC97DFFAA7CACD52FF913A66911CFF074172F3CB0934E"
}

Pointer: 
- --------
{
  "pisp-point":
   {
    "url":"http://cannon-ciota.bit/cannon-ciota_publickey.pisp",
    "fingerprint":"2BB515CD66E74E2845DC6494A5A22879"
   }
}

or optionally we can use a hashsum of the pointed file in case the
file contains more fields than just the public key, to allow for
future extensions to PISP proposed standard.

{
  "pisp-point":
   {
    "url":"http://cannon-ciota.bit/cannon-ciota_publickey.pisp",
    "sha256":"5580aaa1a28145a1ec6c4136af58bdafb23fc13dbdb820ef1da7753e9f744f7d"
   }
}

Contents of cannon-ciota_publickey.pisp:
- ----------------------------------------
 {
   "pisp-pub":"026D3CA82768BC8D8E512EC97DFFAA7CACD52FF913A66911CFF074172F3CB0934E"
}

	Whenever looking up someone’s PISP public key from their
	namecoin identity, the client would first search for the
	pisp-pub (PISP public key) field, and if not found will proceed
	to search for the pointer field denoted as pisp-point (PISP
	pointer). The PISP pointer field would have the location of the
	public key used for PISP along with the fingerprint, or hashsum
	of the pointed file. The contents of the file mentioned in the
	pointer field would have the public key in the same JSON format
	as would be if directly in the namecoin datastore. Reason why
	is to allow the enabling of any future extensions to the PISP
	proposed standard.  PISP would be opt in. To opt in one would
	simply include a field in their namecoin identity to advertise
	their PISP public key, using either pisp-pub or pisp-point.
	For purpose of demonstration we will assume Alice and Bob both
	have a PISP public key included in their namecoin ID. Bob
	wants his phone number listed in his namecoin identity so
	his contacts can reach him, even if his phone number changes
	frequently. However Bob only wants specific contacts to know
	his current personal phone number, and Bob may want a seperate
	group of contacts to know his business phone number. Bob may
	also have another phone number that is public. And so Bob's
	phone entry in his namecoin ID might look like the following

{
   "phone":
   {
    "pisp":"http://EXAMPLE.URL/bobs-phone.pisp"
   }
}

or for multiple phones

{
   "phone":
   {
    "public":"+99 1234567890", 
    "business":
      {
		"pisp":"http://EXAMPLE.URL/bobs-business-phone.pisp"
      },
    "personal":
      {
		"pisp":"http://EXAMPLE.URL/bobs-phone.pisp"
      }
   }
}

	The .pisp file would have the relevant information but
	encrypted to the pisp public key of each of the contacts Bob
	authorizes to have access to such information. To prevent Bob's
	connections from being revealed each encrypted data snippet
	(one per contact) would not list public keys, only encrypted
	data. And so any contact would have to attempt to decrypt
	each snippet within the .pisp file until it finds a snippet
	it is able to decrypt. As a result outsiders cannot determine
	whom Bob's connections are, only the number of authorized
	connections. One mitigation to advertising number of authorized
	contacts would be to pad the .pisp file with decoy snippets. As
	a precaution against bruteforcing data to matching cypher text
	each snippet would also include a random salt unique for each
	snippet before encrypting.  And so if Bob wanted his number
	visible to Alice, he would include his current phone number
	(with a random salt) encrypted to Alice's listed PISP key and
	include the encrypted snippet into his .pisp file referenced
	in his namecoin identity. Alice's addressbook app on her phone
	would automatically lookup Bob's number from his namecoin ID,
	after seeing it as not publicly viewable but protected by
	PISP it would then use Alice's private PISP key to attempt to
	decrypt each snippet in Bob's .pisp file until successfully
	decrypting a snippet which then reveals Bob's number to Alice.
	If Bob's PISP protected phone number is not visible to Alice,
	after finding no decipherable snippet the app can tell Alice
	"not authorized to view this information". Alice then can
	hit a button on her app such as "request contact info for
	Bob's phone" which would send a request to Bob through a
	communications channel (such as publically listed email
	address or bitmessage address in Bob's namecoin ID) which
	would request Bob to include Alice as an authorized contact
	for that specified piece of information (in this case, Bob's
	personal number). The request would be signed by Alice's
	PISP key before being encrypted to Bob's PISP key to protect
	from spoofing and to maintain confidentiality of both the
	contents and identity of requester, to anyone who is not Bob.
	Upon receiving such request, Bob can choose to either allow
	Alice access or ignore such request. Because denying access
	is passive rather than active unlike granting access, this
	provides plausible deniability for Bob. If Bob chooses to
	not allow Alice as an authorized contact to view his number,
	he simply does nothing which provides plausible deniability
	of Bob's decision as Alice would not know if Bob explicitly
	chose to not to acknowledge request, or if Bob simply just
	forgot, or did not read the request.

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cassini
Posts: 326
Joined: Sun May 26, 2013 6:36 pm

Re: PISP: Proposed solution for selective information sharin

Post by cassini » Wed Jan 25, 2017 3:23 pm

Very interesting application use-case of the Namecoin blockchain. This could be a solution to the problem of how to control read-access to individial parts of one's public profile on the blockchain.
I haven't looked at the security implications of the intended protocol, yet. If there are any security issues then they should be easily solvable, though.

Have you already created an up-to-date example for a JSON record containing a pisp field on the blockchain? Your existing id records (i.e. id/cannon) contain malformed JSON data: the outermost bracket is missing. Furthermore, the many linefeed characters ("\n") may cause JSON parsers run into problems in the future (although currently allowed by the JSON specs).

biolizard89
Posts: 1932
Joined: Tue Jun 05, 2012 6:25 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by biolizard89 » Sun Jan 29, 2017 8:03 am

Hi Cannon,

Very interesting proposal. Apologies for my delayed response.

A few comments:

What algorithm is used for the fingerprint field? How could that algorithm be changed later? (You use both "sha256" and "fingerprint" as JSON fields here, apparently for similar purpose. SHA256 hashes of public keys are commonly called fingerprints.)

What protection is there against the names of phone numbers being revealed (the "business" and "personal" labels in your example)? I suspect that attacks could be mounted that perform metadata analysis against these labels (including when they change). Maybe encrypt them as well, so that Alice has to try to decrypt each phone number and when she finds one that is decryptable, she learns the label too?

What protection is there against the number of phone numbers being revealed? I suspect that using decoys might not be sufficient to hide it against statistical attacks. It might be interesting to use a merkle tree for this. I can't think of a way to do so without requiring Bob to tell Alice the merkle branch proof when he grants her access, though.

Finally, I'm honestly not very familiar with what existing proposals exist in this space. I would be surprised if no one has previously tried to solve this use case. Any idea?

Cheers!
Jeremy Rand, Lead Namecoin Application Engineer
NameID: id/jeremy
DyName: Dynamic DNS update client for .bit domains.

Donations: BTC 1EcUWRa9H6ZuWPkF3BDj6k4k1vCgv41ab8 ; NMC NFqbaS7ReiQ9MBmsowwcDSmp4iDznjmEh5

cannon-c
Posts: 7
Joined: Wed Jan 25, 2017 10:05 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by cannon-c » Tue Feb 07, 2017 7:25 pm

biolizard89 wrote: What algorithm is used for the fingerprint field? How could that algorithm be changed later?
No specific algorithm used in the examples of this draft proposal. That could be determined with more discussion as for what to use for fingerprint fields and keys.
biolizard89 wrote: How could that algorithm be changed later?
hmm for keys maybe add a label to the key entry to indicate what type it is? Or I wonder how easily a client software could detect what is being used.
biolizard89 wrote: (You use both "sha256" and "fingerprint" as JSON fields here, apparently for similar purpose. SHA256 hashes of public keys are commonly called fingerprints.)
I used "sha256" and "fingerprint" separate on purpose to distinguish between their purpose. The idea is that "fingerprint" is referring to hash of the key, whereas "sha256" is referring to the hash of the pointed data which may contain more than just a key.
biolizard89 wrote: What protection is there against the names of phone numbers being revealed (the "business" and "personal" labels in your example)? I suspect that attacks could be mounted that perform metadata analysis against these labels (including when they change). Maybe encrypt them as well, so that Alice has to try to decrypt each phone number and when she finds one that is decryptable, she learns the label too?
That is a good point. I like the idea of ability to encrypt label also so long as it is optional. In the example I used I have the labels of the phone entry (business, personal, etc...) public with the contents being a pointed to encrypted snippets. However if I wanted to encrypt a label also, I could just have those hidden labels encrypted within the data snippets as you mentioned, in my "phone" entry of my namecoin ID I would include a referenced .pisp file with a blank label. The entry that contains no label would indicate that it is for purposes of storing phone numbers with corresponding encrypted labels.
biolizard89 wrote: What protection is there against the number of phone numbers being revealed? I suspect that using decoys might not be sufficient to hide it against statistical attacks. It might be interesting to use a merkle tree for this. I can't think of a way to do so without requiring Bob to tell Alice the merkle branch proof when he grants her access, though.
Would need to take some thinking to determine possible statistical attacks and counter measures.
biolizard89 wrote: Finally, I'm honestly not very familiar with what existing proposals exist in this space. I would be surprised if no one has previously tried to solve this use case. Any idea?
I am curious about other alternative solutions. This is a huge need especially for public directories, I have not seen anything yet for this use case hence why I typed this up.
Cannon
Namecoin ID: cannon

cannon-c
Posts: 7
Joined: Wed Jan 25, 2017 10:05 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by cannon-c » Tue Feb 07, 2017 7:30 pm

I think I forgot to mention in the draft, that obviously all .pisp files or any referenced external data should be either signed and/or hashsum of it included in the namecoin ID for verification purposes.
Cannon
Namecoin ID: cannon

cannon-c
Posts: 7
Joined: Wed Jan 25, 2017 10:05 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by cannon-c » Tue Feb 07, 2017 7:44 pm

cassini wrote: Have you already created an up-to-date example for a JSON record containing a pisp field on the blockchain? Your existing id records (i.e. id/cannon) contain malformed JSON data: the outermost bracket is missing.
Thanks. I will be updating it soon and when I do so will include an embedded pisp example.
cassini wrote: Furthermore, the many linefeed characters ("\n") may cause JSON parsers run into problems in the future (although currently allowed by the JSON specs).
If you are referring to the post I only formatted that way to make it easy for humans to read. If you are referring to my namecion ID then yes it will get corrected soon.
Cannon
Namecoin ID: cannon

biolizard89
Posts: 1932
Joined: Tue Jun 05, 2012 6:25 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by biolizard89 » Wed Feb 15, 2017 2:44 pm

Would you like me to ask Joachim from Jolocom to take a look at this proposal and give feedback? I met Joachim at DWS 2016; Cassini subsequently met him at GETD#4. It seems like a topic for which Joachim may be familiar with prior work (or perhaps the lack thereof).
Jeremy Rand, Lead Namecoin Application Engineer
NameID: id/jeremy
DyName: Dynamic DNS update client for .bit domains.

Donations: BTC 1EcUWRa9H6ZuWPkF3BDj6k4k1vCgv41ab8 ; NMC NFqbaS7ReiQ9MBmsowwcDSmp4iDznjmEh5

cannon-c
Posts: 7
Joined: Wed Jan 25, 2017 10:05 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by cannon-c » Sat Feb 18, 2017 12:00 am

biolizard89 wrote:Would you like me to ask Joachim from Jolocom to take a look at this proposal and give feedback? I met Joachim at DWS 2016; Cassini subsequently met him at GETD#4. It seems like a topic for which Joachim may be familiar with prior work (or perhaps the lack thereof).
Yeah sure, would be interesting to see what his input is on this, or if there are other currently working things of similar nature.


Perhaps may want to refer him to this forum link due to the proposal being very draft version. (Hence why I posted it here for further input). And since comments on this thread mentions something I forgot to include in the draft, that all .pisp files or any referenced external data should be either signed and/or hashsum of it included in the namecoin ID for verification purposes. Along with more clarifications brought forth in this thread.

Unless you think we should first update the draft write up before forwarding to him.
Cannon
Namecoin ID: cannon

biolizard89
Posts: 1932
Joined: Tue Jun 05, 2012 6:25 am
os: linux

Re: PISP: Proposed solution for selective information sharin

Post by biolizard89 » Sun Mar 19, 2017 3:16 am

cannon-c wrote:
biolizard89 wrote:Would you like me to ask Joachim from Jolocom to take a look at this proposal and give feedback? I met Joachim at DWS 2016; Cassini subsequently met him at GETD#4. It seems like a topic for which Joachim may be familiar with prior work (or perhaps the lack thereof).
Yeah sure, would be interesting to see what his input is on this, or if there are other currently working things of similar nature.


Perhaps may want to refer him to this forum link due to the proposal being very draft version. (Hence why I posted it here for further input). And since comments on this thread mentions something I forgot to include in the draft, that all .pisp files or any referenced external data should be either signed and/or hashsum of it included in the namecoin ID for verification purposes. Along with more clarifications brought forth in this thread.

Unless you think we should first update the draft write up before forwarding to him.
I've sent Joachim a link to this forum thread.
Jeremy Rand, Lead Namecoin Application Engineer
NameID: id/jeremy
DyName: Dynamic DNS update client for .bit domains.

Donations: BTC 1EcUWRa9H6ZuWPkF3BDj6k4k1vCgv41ab8 ; NMC NFqbaS7ReiQ9MBmsowwcDSmp4iDznjmEh5

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