CH716280A2 - A method of processing, in an enclave, encrypted computer data by means of an encrypted application containing an executable. - Google Patents

Abstract

The invention relates to a method for processing computer data (12) contained in a first encrypted container (16), by means of a third-party application (14) contained, in the form of an executable file, in a second container (18). ) encrypted, this processing being carried out within a cryptographic enclave (5) in which the containers (16, 18) are decrypted to allow the execution of the application (14) thus decrypted on the data (12) thus decrypted .

Description

TECHNICAL AREA

The invention relates to the field of computing, and more specifically to the field of processing computer data by means of an application.

PRIOR ART

A computer program comprises instructions by means of which, by means of a processing unit, operations are carried out on input data, to provide, from these- ci, output data or result.

[0003] Mass data processing (in English big data) is tending to industrialize. Specialized programs scrutinize the data flows (in particular the personal data of users) circulating on the Web, analyze this data, perform calculations (in particular statistics) and then store their results in databases for the purposes of subsequent exploitation (especially commercial).

To prevent their personal data from being used without their authorization, or to maintain relative anonymity on the Web, some users take the precaution of encrypting them.

[0005] Some data are moreover (or should be) the subject of systematic encryption, because of their confidential nature (typically health data or financial data), the bodies responsible for their management (hospitals, banks) being subject to professional secrecy obligations, and as such responsible for any use that may be made of it by unauthorized third parties.

[0006] The encrypted data is however inaccessible - and therefore unusable - for those who do not have an appropriate cryptographic key allowing their decryption.

However, there are many cases where the owner of the data (typically a patient of a medical institute or a client of a bank) may wish, under conditions, to authorize an interested third party to process the data, without however, communicate the decryption key to this third party, nor authorize him to fully access the data when only part of this data is likely to interest him.

Conversely, the interested third party may wish to keep secret, vis-à-vis still other third parties, its own analysis routines, and encrypt the programmatic data (including in the form of executables) of its applications, including development is the result of precious know-how.

The invention aims to offer a solution to these problems, by proposing a method of processing encrypted data which allows both an application to process this data without affecting their confidentiality, and the application itself to remain confidential.

SUMMARY OF THE INVENTION

A method is proposed for processing computer data by means of a third-party application in the form of an executable file, this method comprising the operations consisting in: <tb> <SEP> - Encrypt the data to be processed to form a first encrypted data container; <tb> <SEP> - Store separately the first encrypted container and a first decryption cryptographic key thereof; <tb> <SEP> - Encrypt the executable file of the third party application to form a second encrypted container; <tb> <SEP> - Store separately the second container and an associated second cryptographic decryption key; <tb> <SEP> - On receipt of a data processing request by the third-party application, select a computer processing unit in which an execution environment secured by cryptography, called an enclave, is implemented; <tb> <SEP> - Instantiate the enclave; <tb> <SEP> - Load into the enclave the first container and the associated first cryptographic decryption key, as well as the second container and the associated second cryptographic decryption key; <tb> <SEP> - In the enclave: <tb><SEP> <SEP> o Decrypt the data of the first container using the first cryptographic decryption key; <tb><SEP> <SEP> o Decrypt the executable file of the third-party application contained in the second container, using the second cryptographic decryption key; <tb><SEP> <SEP> o Run the third-party application on the data thus decrypted; <tb> <SEP> - Outside the enclave, store the result of this execution on a predefined memory location.

BRIEF DESCRIPTION OF THE FIGURES

[0011] Other objects and advantages of the invention will become apparent in the light of the description of an embodiment, given below with reference to the accompanying drawings in which: <tb> <SEP> LaFIG.1 is a simplified diagram illustrating a computer network of which at least one node is equipped with a processing unit on which an enclave is implemented; <tb> <SEP> LaFIG.2 is a functional diagram illustrating the storage of encrypted data to be processed and of an also encrypted application; <tb> <SEP> LaFIG.3 is a functional diagram illustrating the processing of data by the application.

DETAILED DESCRIPTION OF THE INVENTION

The proposed method aims to treat, confidentially, computer data by means of a third-party application (that is to say from a publisher separate from the sender of the data).

This processing can be carried out within a computer network (which, as illustrated, can be of the peer-to-peer type) comprising a plurality of nodes2 (computers, servers).

The proposed processing method uses in particular the technology of the secure execution environment or, in English terminology, of the trusted execution environment (TEE).

By reference to theFIG.1, a secure execution environment (Trusted execution environment or TEE) is, within a computer processing unit3 equipping a node2and provided with a processor or CPU (Central Processing Unit) 4, a temporary space for computing and storing data, called (by convention) an enclave, or even a cryptographic enclave, which is isolated, by cryptographic means, from any unauthorized action resulting from the execution of an application outside this space , typically of the operating system.

[0016] Intel®, for example, from 2013 revised the structure and interfaces of its processors to include enclave functions, under the name Software Guard Extension, better known by the acronym SGX. SGX equips most of the XX86 type processors marketed by Intel® since 2015, and more specifically from the sixth generation incorporating the so-called Skylake microarchitecture. The enclave functions offered by SGX are not automatically accessible: they must be activated via the elementary input / output system (Basic Input Output System or BIOS).

It does not fall within the requirements of the present description to detail the architecture of the enclaves, insofar as: Despite its relative youth, this architecture is relatively well documented, in particular by Intel® which has filed numerous patents, cf. e.g., among the most recent, the US patent application US 2019/0058696; Processors making it possible to implement them are available on the market - in particular the aforementioned Intel® processors; Only the functionalities allowed by the enclave are of interest to us here, these functionalities being able to be implemented via specific command lines. As such, those skilled in the art may refer to the guide published in 2016 by Intel®: Software Guard Extensions, Developer Guide.

[0018] For a more accessible description of the enclaves, and more particularly of Intel® SGX, those skilled in the art can also refer to A. Adamski, Overview of Intel SGX - Part 1, SGX Internal, or to D. Boneh , Nickaming Schemes, Fast Verification, and Applications to SGX Technology, in Topics in Cryptology, CT - RSA 2017, The Cryptographers' Track at the RSA Conférence 2017, San Francisco, CA, USA, Feb. 14-17, 2017, Proceedings, pp. 149-164, or to K. Severinsen, Secure Programming with Intel SGX and Novel Applications, Thesis submitted for the Degree of Master in Programming and Networks, Dept. Of Informatics, Faculty of Mathematics and Natural Science, University of Oslo, Autumn 2017.

To summarize, with reference to theFIG.1, an enclave5 comprises, first of all, a secure memory zone (called Enclave Page Cache, in English Enclave Page Cache or EPC), which contains code and data relating to the 'enclave itself, and whose content is encrypted and decrypted in real time by a dedicated chip called the Memory Encryption Engine (MEE). The EPC6 is implemented within a part of the dynamic random access memory (DRAM) 7 allocated to the processor4, and to which ordinary applications (in particular the operating system) do not have access.

[0020] The enclave5 comprises, secondly, cryptographic keys used to encrypt or sign on the fly the data leaving the EPC6, whereby the enclave5 can be identified (in particular by other enclaves), and the The data it generates can be encrypted to be stored in unprotected memory areas (ie outside of EPC6).

In order to be able to operate such an enclave5, an application8 must be segmented into, on the one hand, one or more unsecured parts9 (in English untrusted part (s)), and, on the other hand, one or more secure parts10 (in English trusted part (s)).

Only the processes induced by the secure part (s) of the application8 can access the enclave5. The processes induced by the unsecured part (s) 9 cannot access the enclave5, that is to say, they cannot dialogue with the processes induced by the part (s) (s) 10secure (s).

The creation (also called instantiation) of the enclave5 and the flow of processes within it are controlled via a set of particular instructions executable by the processor4et called by the part (s) 10secure (s) of the application8.

[0024] Among these instructions: ECREATE commands the creation of an enclave5; EINIT commands the initialization of the enclave5; EADD commands the code loading into the enclave5; ERESUME commands a new execution of code in the enclave5; EEXIT controls the exit of enclave5, typically at the end of a process running in enclave5.

We have, on theFIG.1, functionally represented the enclave 5 in the form of a block (in dotted lines) encompassing the secure part of the application8, the instruction set of the processor4, and the EPC6 . This representation is not realistic; it simply aims to visually bring together the main elements that make up or operate the enclave5.

[0026] We will explain below how the enclaves are exploited.

As can be seen in laFIG.1, there is shown data12 to be processed in the form of a file. These data12 may be in the form of one or more computer files. The data12 can be structured, e.g. in the form of database files, forms, spreadsheets, documents. It can also be raw, unstructured data.

These data12sont created, or temporarily stored, in clear (that is to say in unencrypted form), within a terminal13dit transmitter, connected to a network1.

The data processing is intended to be carried out by means of an application14tierce which is in the form of a code file directly executable by a processor (simply called an "executable").

The application14 is created (or edited), or temporarily stored, in clear (that is to say in unencrypted form), within a terminal15 said editor, connected to a network1 (which may be the same than the one to which the transmitter is connected13).

Before being stored on the network1 for future processing, the data12 is first encrypted to form a first encrypted container16 of data. The decryption of the first encrypted container can only be carried out by means of a first decryption cryptographic key. According to a particular embodiment, a single key 17 is used for both the encryption and the decryption. In this case, the encryption is said to be symmetric.

In the example illustrated, the encryption is carried out within the transmitter terminal13.

Once the data12 has been encrypted, the first container16 and the first decryption key17 are stored separately (here on distinct nodes2 of the network1).

Likewise, before being stored on the network1 for future use, the executable file of the application14 is first encrypted to form a second encrypted container18. The decryption of the second encrypted container can only be achieved by means of a second decryption cryptographic key. According to a particular embodiment, a single key 19 is used for both encryption and decryption. In this case, the encryption is said to be symmetric.

In the example illustrated, the encryption is carried out within the terminal15 éditeur.

Once the application14 has been encrypted, the second container18 and the second decryption key19 are stored separately (here on distinct nodes2 of the network1).

The processing of the data12 can be requested, on request, by a user (who can be the editor15). In this case, a data processing request12 by application14 is sent by the user.

To carry out this processing, a first operation consists, on receipt (by the network1) of the data processing request12, in selecting a computer processing unit (eg equipping a node2 of the network1) on which an enclave5 is implemented.

A second operation consists in instantiating the enclave5.

A third operation consists in loading into the enclave5 (preferably via secure communication lines, typically using the Transport Layer Security or TLS protocol): The first container16 and the first decryption cryptographic key17 associated with it; The second18container and the second decryption cryptographic key19 associated with it.

To this end, the enclave5est advantageously provided, from its instantiation, with a communication interface21de emulation supporting the chosen protocol (here TLS) for the exchange of secure data.

A fourth operation consists, in the enclave5, in decrypting the data of the first container16 by means of the first key17de decryption. At the end of this operation, the data12 are accessible in clear in the enclave5 (but not from outside it).

For this purpose, the enclave5est advantageously provided with a decryption module22.

A fifth operation consists, in the enclave5, in decrypting the executable file of the application14tierce contained in the second container18, by means of the second decryption key19. This operation is here performed by the decryption module 22. At the end of this operation, the application 14 is accessible in clear in the enclave5 (but not from outside it).

A sixth operation then consists in executing the application14 thus decrypted on the data12 thus decrypted. This operation is advantageously carried out by a calculation module with which the enclave5 is provided.

The execution of the application14 on the data produces a result24. This result24 is stored, outside the enclave5, on a predefined memory location. In the example illustrated, the result24 is transmitted by a node2 of the network.

Thanks to this method, the data 12 can be analyzed without being available in the clear outside the enclave 5, to which third parties do not have access. In addition, the data12 is not communicated to the publisher15 for it to carry out its application itself14. The editor15 therefore does not have the data12: it only has the result provided by the execution of its application14. This results in maintaining the confidentiality of data12, including vis-à-vis third parties who wish (and may be authorized to) analyze them.

Likewise, the application14 is not known to third parties (or can be copied by them) either, despite its availability for the processing of data12 in the enclave8. The result is that the publisher15 is copy protected while being able to process the data12 when authorized to do so.

Claims (1)

1. A method of processing computer data (12) by means of a third-party application (14) in the form of an executable file, this method comprising the operations of: - Encrypt the data (12) to be processed to form a first encrypted data container (16); - Separately storing the first encrypted container (16) and a first cryptographic key (17) for decryption thereof; - Encrypt the executable file of the third-party application (14) to form a second encrypted container (18); - Separately store the second container (18) and a second associated cryptographic decryption key (19); - On receipt of a data processing request (12) by the third-party application (14), select a computer processing unit (3) in which an execution environment secured by cryptography, called an enclave (5) is implemented ; - Instantiate the enclave (5); - Loading into the enclave (5) the first container (16) and the first associated cryptographic decryption key (17), as well as the second container (18) and the second associated cryptographic decryption key (19); - In the enclave (5): o Decrypt the data (12) of the first container (16) by means of the first cryptographic decryption key (17); o Decrypt the executable file of the third-party application (14) contained in the second container (18), by means of the second cryptographic decryption key (19); o Execute the third-party application (14) on the data (12) thus decrypted; - Outside the enclave (5), store the result (24) of this execution on a predefined memory location.