PublicKey Info Base » History » Revision 8
Revision 7 (Yingdi Yu, 07/08/2014 05:07 PM) → Revision 8/79 (Yingdi Yu, 07/08/2014 05:13 PM)
Public key Info Base (PIB) Service
==================================
## Public Key Info Management
NDN data packets are secured through digital signatures.
In order to generate a valid signature, an NDN application needs to know not only the correct key to use but also the correct public key information that should be put into the `KeyLocator` of a data packet.
The information needs to be managed locally on the system where the application is running.
The information related to keys is managed at three granularities: identities, keys, and certificates.
A key is always associated with a namespace, called "identity".
An identity however may have more than one keys.
Each key is named as `/<Identity>/[KeyId]`.
The `KeyId` uniquely identifies a key which belongs to the `Identity`.
Among these keys, only one is the default key of the identity.
If only identity is provided when signing a packet, the default key of the identity will be used to sign the packet.
A certificate is always associated with the key in the certificate
If a certificate is provided when signing a packet, the corresponding private key should be used to sign the packet
and the name of the certificate name may be put into the `KeyLocator` of the packet.
A key may have more than one certificates (e.g., certificates may be issued by different parties).
Among these certificates, only one is the default certificate of the key.
The default certificate of the default key of an identity is the default certificate of the identity.
If only identity is provided when signing a packet, the name of the default certificate of the identity may be put into the `KeyLocator` of the packet.
All the information above may be accessed by different APIs and applications on the same system,
therefore it is desirable to make the information provisioning as a system service.
Since public keys and certificates are supposed to be publicly available,
the service also serves as a local storage of certificate and public keys,
besides providing the public key related information.
## PIB management model
The public key information of each system user is managed separately in PIB.
For now, PIB service is a system service (i.e., run by root).
PIB service may be separated into several user services (i.e., run by each user) in the future.
Each user has three tables in PIB: identity table, key table, and certificate table.
The public key information of a user is managed in these tables.
Identity table consists of two columns: `identity` (primary key) and `default_key_id`.
Key Table consists of five columns: `identity`, `key_id`, `key_type`, `key_bits`, and `default_cert_name`.
The combination of `identity` and `key_id` is the primary key of key table.
Certificate table consists of four columns: `certificate_name` (primary key), `identity`, `key_id`, and `certificate_data`.
Besides the tables for each user, PIB has two more management tables: user table and certificate_publishing table.
User table stores user's local management key (we will discuss it later) and user's default identity
Each user has its own default identity.
From the default identity, the default key and certificate of the user can be derived.
The read access to a user's public key information is not restricted,
while the write access to a user's public key information requires authentication.
The write access is expressed as signed commands.
The signing key can be authenticated only if the key already exists in the corresponding user's PIB tables.
Each key has its own write access privilege which is defined as:
* The root user has the **root key** of the local system. The root key has the highest privilege, i.e., its owner is allowed to change anything in PIB. The identity of the root key is `/localhost`, and the name of the root key should be `/localhost/[KeyId]`.
* Each user has its own **local management key**. The local management key is allowed to change anything in the user's PIB info including the three tables and user's own entry in the user table. The identity of the user local management key is `/localhost/user/[UserName]`, and the name of the key should be `/localhost/user/[UserName]/[KeyId]`. Note that the local management key of the root user is the root key.
* All the other keys are called **regular keys**. A regular key is allowed to change keys/certificates with identities under the key's own namespace, e.g., a key with the identity `/ndn/ucla/alice` is allowed to change a key with the identity `/ndn/ucla/alice/chat` but is not allowed to change a key with the identity `/ndn/ucla/bob`.
## PIB Service Protocol
PIB service provides an interface to NDN applications for public key info lookup.
The interface is defined in terms of NDN packets (interest/data).
A query to PIB is expressed as a **[signed interest](http://redmine.named-data.net/projects/nfd/wiki/Signed_Interests)**.
The query interest is defined as:
/localhost/pib/[UserName]/[Verb]/[Param]/<signed_interest_security_components>
`UserName` indicates the tables in which the query should apply.
`Verb` indicates the access operation.
Four Three types of operations are defined: `get` (Read), `search` (Read), and `update` (Write), and `delete` (Write).
The operation `get` and `search` are quite similar to each other.
The only difference is that the response to `get` is the queried entity per se while the response to `search` operation is the existence (a boolean value) of the queried entity.
`Param` is a TLV block containing parameters of the query.
Different types of operations have their own parameters.
### `Get` Parameters
For `get` operation, `Param` is defined as:
GetParam := Type
Filter
Filter := Name | DefaultOf | ListOf
DefaultOf := EntityDesc
ListOf := EntityDesc
EntityDesc := Type
Name
Type := ID | KEY | CERT
`Type` indicates which table the query will be applied eventually.
`Filter` indicates how to apply the query.
When `Name` is specified in `Filter`, PIB will directly lookup the entry with the same name in the table indicated by `Type`.
When `DefaultOf` is specified in `Filter`, PIB will first derive the name of the target through the default information and lookup the entry in the table indicated by `Type`.
When `ListOf` is specified in `Filter`, PIB will collect all the entries that satisfy the condition specified in `ListOf`.
Here are some examples of `GetParam`:
GetParam
{
Type: KEY
Filter
{
Name: /ndn/edu/ucla/ksk-1234
}
}
The example above is a query to get a key with the name `/ndn/edu/ucla/ksk-1234`.
GetParam
{
Type: CERT
Filter
{
DefautOf
{
Type: ID
Name: /ndn/edu/ucla/alice
}
}
}
The example above is a query to get the default certificate of an identity `/ndn/edu/ucla/alice`.
GetParam
{
Type: CERT
Filter
{
ListOf
{
Type: KEY
Name: /ndn/edu/ucla/ksk-1234
}
}
}
The example above is a query to get a list of certificates of a key `/ndn/edu/ucla/alice`.
### `Search` Parameters
The parameters of `search` operation is quite similar to `get` operation except that there is no `ListOf` filter.
SearchParam := Type
Filter
Filter := Name | DefaultOf
DefaultOf := EntityDesc
EntityDesc := Type
Name
Type := ID | KEY | CERT
### `Update` Parameters
The parameters of `update` operation are defined as:
UpdateParam := Entity
DefaultOpt
Entity := Identity | PublicKey | Certificate
Identity := Name
PublicKey := Name
Bytes
Certificate := Bytes
DefaultOpt := USER_DEFAULT | ID_DEFAULT | KEY_DEFAULT | NO_DEFAULT
The operation, once validated, will add a new entry in the corresponding table if no such an entry exists or update the existing entry,
and change the default setting according to `DefaultOpt`.
### `Delete` Parameters
The parameters of `delete` operation are defined as:
DeleteParam := EntityDesc
EntityDesc := Type
Name
Type := ID | KEY | CERT
The operation, once validated, will add a new entry in the corresponding table if no such an entry exists or update the existing entry,
and change the default setting according to `DefaultOpt`.
### TLV-TYPE assignments
Type | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
GetParam | 128 | 0x80
SearchParam | 129 | 0x81
UpdateParam | 130 | 0x82
DeleteParam Type | 131 | 0x83
Type Filter | 132 | 0x84
Filter Name | 133 | 0x85
Name DefaultOf | 134 | 0x86
DefaultOf ListOf | 135 | 0x87
ListOf | 136 | 0x88
EntityDesc | 137 144 | 0x89 0x90
Entity | 138 145 | 0x8a 0x91
Identity | 139 146 | 0x8b 0x92
PublicKey | 140 147 | 0x8c 0x93
Certificate | 141 148 | 0x8d 0x94
Bytes | 142 149 | 0x8e 0x95
DefaultOpt | 143 150 | 0x8f 0x96
### Constant value assignments
For type `Type`:
Constant | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
ID | 0 | 0x00
KEY | 1 | 0x01
CERT | 2 | 0x02
For type `DefaultOpt`:
Constant | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
NO_DEFAULT | 0 | 0x00
USER_DEFAULT | 1 | 0x01
ID_DEFAULT | 2 | 0x02
KEY_DEFAULT | 3 | 0x03