Causal total order broadcast protocols using trusted execution environments

A Byzantine fault-tolerant, distributed computerized system to execute a causal total order broadcast (CTOB) protocol, the system comprising:

• a set of nodes configured to act as servers for clients of the system, wherein
• each of the nodes is further configured to provide a trusted execution environment and execute a trusted proxy client (TPC) process, in this trusted execution environment, and
• the TPC process is designed such that, in operation, executing the TPC process causes, for each client request received from any of the clients, the client request comprising encrypted contents, to:
• sign the client request;
• invoke a total order broadcast (TOB) protocol, to obtain a sequence number for the signed request, for the nodes to establish a total order in which the signed request will be processed by the nodes;
• and
• upon determining that the signed request is assigned this sequence number as per the TOB protocol, reveal a decrypted version of the encrypted contents of the client request to said each of the nodes, for the latter to be able to further process it according to the TOB protocol;
• wherein said each client request received comprises, in addition to said encrypted contents, a one-time identifier of said each request, and
• executing the TPC process to:
• identify a cryptographic key associated with the one-time identifier, via an association;
• and
• use the identified cryptographic key to decrypt said encrypted contents and obtain said decrypted version, wherein said one-time identifier is a non-encrypted one-time identifier of said each request;
• wherein said each client request received further comprises, in addition to said encrypted contents and the non-encrypted one-time identifier of said each request, an encrypted one-time identifier of a next request;
• use the identified cryptographic key to decrypt said encrypted one-time identifier of the next request, in addition to decrypting said encrypted contents;
• and
• store a further association of the decrypted one-time identifier of the next request with a cryptographic key.

A computer program product to execute a trusted proxy client (TPC) process, in a trusted execution environment, to implement a causal total order broadcast (CTOB) protocol, in a Byzantine fault-tolerant, distributed computerized system comprising a set of nodes configured to act as servers for clients of the system, each of the nodes being further configured to provide such a trusted execution environment and execute such a TPC process in such a trusted execution environment, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by processing means of each of one or more of the nodes, so as to cause the processing means to execute such a TPC process in such a trusted execution environment and thereby cause the TPC process, upon execution, to:

• sign the client request;
• invoke a total order broadcast protocol, or TOB protocol, to obtain a sequence number for the signed request, for the nodes to establish a total order in which the signed request will be processed by the nodes;
• and
• upon obtaining a proof that the signed request is assigned this sequence number as per the TOB protocol, reveal a decrypted version of the encrypted contents of the client request to said each of the nodes, for the latter to be able to further process it according to the TOB protocol;
• wherein said each client request received comprises, in addition to said encrypted contents, a one-time identifier of said each request, and
• executing the TPC process to:
• identify a cryptographic key associated with the one-time identifier, via an association;
• and
• use the identified cryptographic key to decrypt said encrypted contents and obtain said decrypted version, wherein said one-time identifier is a non-encrypted one-time identifier of said each request;
• wherein said each client request received further comprises, in addition to said encrypted contents and the non-encrypted one-time identifier of said each request, an encrypted one-time identifier of a next request;
• use the identified cryptographic key to decrypt said encrypted one-time identifier of the next request, in addition to decrypting said encrypted contents;
• and
• store a further association of the decrypted one-time identifier of the next request with a cryptographic key.

A method of executing a causal total order broadcast (CTOB) protocol, in a Byzantine fault-tolerant, distributed computerized system comprising a set of nodes acting as servers for clients of the system, comprising:

• each of the nodes hosts a trusted proxy client (TPC) process, the trusted proxy client process executing in a trusted execution environment of said set of nodes, and
• the TPC process comprises, for each client request received from any of the clients, the client request comprising encrypted contents:
• signing the client request;
• invoking a total order broadcast (TOB) protocol, to obtain a sequence number for the signed request, whereby the nodes establish a total order in which the signed request will be processed by the nodes;
• and
• upon determining that the signed request is assigned this sequence number as per the TOB protocol, revealing a decrypted version of the encrypted contents of the client request to said set of nodes, for the latter to be able to further process it according to the TOB protocol, wherein the TPC process further comprises validating said each client request according to a validation protocol imposed by the computerized system, prior to invoking the TOB protocol to obtain the sequence number for the signed request.

A method of executing a causal total order broadcast (CTOB) protocol, in a Byzantine fault-tolerant, distributed computerized system comprising a set of nodes acting as servers for clients of the system, comprising:

• each of the nodes hosts a trusted proxy client (TPC) process, the trusted proxy client process executing in a trusted execution environment of said set of nodes, and
• the TPC process comprises, for each client request received from any of the clients, the client request comprising encrypted contents:
• signing the client request;
• invoking a total order broadcast (TOB) protocol, to obtain a sequence number for the signed request, whereby the nodes establish a total order in which the signed request will be processed by the nodes;
• and
• upon determining that the signed request is assigned this sequence number as per the TOB protocol, revealing a decrypted version of the encrypted contents of the client request to said set of nodes, for the latter to be able to further process it according to the TOB protocol, wherein said each client request comprises an encrypted identifier, and
• the TPC process further comprises, for said each client request:
• decrypting said encrypted identifier, in addition to decrypting the encrypted contents;
• and
• revealing to said each of the nodes, based on the decrypted identifier and upon obtaining said proof, an identity of a client corresponding to said each request, in addition to revealing the decrypted version of the encrypted contents.