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and SPKI

and SPKI. Vishwas Patil STCS, TIFR, Mumbai, INDIA vtp@tifr.res.in http://www.tcs.tifr.res.in/~vishwas. What is E ?. E is a simple, secure, distributed, pure-object, persistent programming language. E blends the lambda calculus, capability security, and modern cryptography.

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and SPKI

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  1. and SPKI Vishwas Patil STCS, TIFR, Mumbai, INDIA vtp@tifr.res.in http://www.tcs.tifr.res.in/~vishwas

  2. What is E? • E is a simple, secure, distributed, pure-object, persistent programming language. • E blends the lambda calculus, capability security, and modern cryptography. • It has two parts: ELib and ELanguage • ELib provides the stuff that goes on between objects. • The ELanguage can be used to express what happens within an object. • E providescryptographic capabilities as an abstraction allowing economy of engineering effort in creating smart contracts.

  3. ELib • A pure-Java library • ELib provides for inter-process capability-secure distributed programming. • Its cryptographic capability protocol enables mutually suspicious Java processes to co-operate safely • And its event-loop concurrency and message pipelining enable high performance deadlock free distributed pure-object computing.

  4. ELanguage • The E language provides a convenient and familiar notation for the ELib computational model • This notation expands into Kernel-E, a minimalist lambda-language much like Scheme or Smalltalk. • Objects written in the E language are only able to interact with other objects according to ELib's semantics, enabling object granularity intra-process security, including the ability to safely run untrusted mobile code (such as caplets).

  5. Kernel-E • The E language is specified in layers. • At the bottom is the Kernel-E language. • The Kernel-E language is a subset of the regular E language • The remainder of E's grammar outside the kernel subset is E's sugar. • The semantics of the sugar is defined by canonical expansion to Kernel-E. • This expansion happens during parsing • E parse trees only contain nodes defined by Kernel-E, so only these are executed by the virtual machine (Java).

  6. ELanguage Grammar • Expressions by precedence and associativity • Primitive Expressions (no precedence needed) • Patterns (including variable declaration) • Quasi-Literal Expressions and Patterns • Methods and Matchers (object behavior) • Lexical Grammar (Tokens)

  7. Perspectives unified under E • Objects [encapsulation, polymorphism, modularity] • Capability Security [constraints] • Cryptographic Protocol [Pluribus] • PKI [SPKI] • Game Rules • Financial Bearer Instruments Granovetter Operator

  8. From Objects to Capabilities • A capability is a pairing of a designated process with a set of services that the process provides • When different capabilities make different behaviors from the same process, we can view the process as a composite and each of its capabilities as a facet • Patterns of Cooperation Without Vulnerability • Only Connectivity Begets Connectivity • By Introduction / Parenthood / Endowment / Initial Conditions • Absolute Encapsulation • All Authority Accessed Only by References • Rights Amplification

  9. Capabilities as a PKI • In SPKI, there is no way of confining the Issuer, to limit the entities that it can authorize. • The lack of a line between Issuer and Subject in the diagram reflects this situation

  10. Capabilities as a PKI contd… • Another difference is that the resource need not be an object. The verifier which checks the authorization acts as a gatekeeper, in the same way that Pluribus acts as a gatekeeper to distributed E objects • In an SPKI system, auditing who performed an action and who authorized it fall naturally out of the public key structure • Auditing in a Pluribus system requires the introduction of intermediary objects accompanying each rights transfer in order to keep track of the authorization path

  11. Capabilities as a PKI contd… • Because an SPKI authorization does not include a direct designation of the resource being authorized, it introduces the possibility of a confused deputy • A confused deputy uses an authorization given to it by one party to access a resource designated by a different party. In so doing, the confused deputy performs an unintended rights transfer • Authorization in SPKI is expensive. • At a minimum each authorization decision requires two signature verification operations by the verifier. • The signature on the certificate must be checked, and the signature of the Subject, proving possession of the private key, must also be checked.

  12. Capabilities as a PKI contd… • In addition, the Subject must sign a challenge from the verifier if the system is to remain safe from replay attacks. • Compare this cost with Pluribus, where the public key operations are limited to connection establishment. • In recognition of this cost, SPKI provides the Certificate Result Certificate which permits an entire certificate chain to be collapsed into one certificate.

  13. Pluribus

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