Python Implementation of NDN-ABS

Following are extensions of the NDN packet format specification regarding signature types.

SignatureSha256WithAbs defines an Attribute-Based signature signature mechanism that is calculated over the SHA256 hash of the Name, MetaInfo, Content, and SignatureInfo TLVs. The signature algorithm is defined in Maji, Hemanta K., Manoj Prabhakaran, and Mike Rosulek. "Attribute-based signatures." Cryptographers’ track at the RSA conference. Springer, Berlin, Heidelberg, 2011..

The TLV-VALUE of SignatureType is 42

KeyLocator is required and must follow the format:

<attribute-authority-prefix>/ABS/42=policy/<attribute-policy>

where

• <attribute-authority-prefix> is an arbitrary name prefix of an attribute authority, provided that <attribute-authority-prefix>/ABS/42=pp/<version> names a data packet that carries public parameters of the authority. This data packet can be further signed by ABS or other types of signature and should be considered trusted based on configured trust schema.

• <attribute-policy> is defined as

    AttributePolicy = Attribute *ExtraAttribute
    ExtraAttribute = BooleanOperator Attribute
  
    Attribute = DIGIT / LCASELETTER / UCASELETTER
    DIGIT = %x30-39 ; 0-9
    LCASELETTER = %x61-7a ; 'a'-'z'
    UCASELETTER = %x41-5a ; 'A'-'Z'
  
    BooleanOperator = "&" / "|"
  

For example,

    /ndn/edu/fiu/ABS/42=policy/student&2019

Represents an ABS policy under /ndn/edu/fiu authority (i.e., there is /ndn/edu/fiu/ABS/42=pp/<version> data packet carrying public parameters of the attribute authority), signing using two attributes combined with "AND" boolean operator: "student" and "2019".

Note attributes are case sensitive: "student" and "Student" refer to different attributes.