Source: http://www.google.com/patents/US7613915?dq=5,973,252
Timestamp: 2016-06-29 17:55:52
Document Index: 205916950

Matched Legal Cases: ['Application No. 60', 'art 200', 'art 200', 'art 200', 'art 200', 'art 200', 'art 200', 'art 200', 'art 200', 'art 200', 'art 300', 'art 300', 'art 300', 'art 600', 'art 600', 'art 600', 'art 600', 'art 600', 'art 600', 'art 600', 'art 700', 'art 700', 'art 700', 'art 700', 'art 700', 'art 700', 'art 700']

Patent US7613915 - Method for programming on-chip non-volatile memory in a secure processor ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsAn improved secure programming technique involves reducing the size of bits programmed in on-chip secret non-volatile memory, at the same time enabling the typical secure applications supported by secure devices. A technique for secure programming involves de-coupling chip manufacture from the later...http://www.google.com/patents/US7613915?utm_source=gb-gplus-sharePatent US7613915 - Method for programming on-chip non-volatile memory in a secure processor, and a device so programmedAdvanced Patent SearchPublication numberUS7613915 B2Publication typeGrantApplication numberUS 11/601,323Publication dateNov 3, 2009Filing dateNov 16, 2006Priority dateNov 9, 2006Fee statusPaidAlso published asEP2084848A2, US8601247, US8621188, US8856513, US20080114984, US20100091988, US20100095125, US20100095134, US20140325240, WO2008057156A2, WO2008057156A3Publication number11601323, 601323, US 7613915 B2, US 7613915B2, US-B2-7613915, US7613915 B2, US7613915B2InventorsPramila Srinivasan, John PrincenOriginal AssigneeBroadOn Communications CorpExport CitationBiBTeX, EndNote, RefManPatent Citations (106), Non-Patent Citations (47), Referenced by (9), Classifications (10), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetMethod for programming on-chip non-volatile memory in a secure processor, and a device so programmed
US 7613915 B2Abstract
An improved secure programming technique involves reducing the size of bits programmed in on-chip secret non-volatile memory, at the same time enabling the typical secure applications supported by secure devices. A technique for secure programming involves de-coupling chip manufacture from the later process of connecting to ticket servers to obtain tickets. A method according to the technique may involve sending a (manufacturing) server signed certificate from the device prior to any communication to receive tickets. A device according to the technique may include chip-internal non-volatile memory to store the certificate along with the private key, in the manufacturing process.
on-chip non-volatile memory including:
a device ID;
an issuer ID;
a first signature;
a certificate generating module coupled to the non-volatile memory configured to:
read the device ID, the private key, the issuer ID, and the first signature from the non-volatile memory;
compute a public key as a function of the private key;
construct a device certificate as a function of the device ID, the issuer ID, the public key, and the first signature;
an interface coupled to the certificate generating module, wherein, in operation, a request for the device certificate is received on the interface, the certificate generating module constructs the device certificate, and the device certificate is sent via the interface in response to the request;
wherein the device is further configured to:
create a temporary key pair having two keys, a temporary public key and a temporary private key, using a number generator;
create an application certificate by signing data including the temporary public key, using a stored private key;
using the temporary private key to compute a second signature as a function of a random number;
wherein the second signature and the random number are sent via the interface in response to the request, along with the device certificate.
2. The device of claim 1, wherein the certificate generating module is further configured to:
compute the public key as a function of the private key and common parameters;
construct the device certificate as a function of the device ID, the issuer ID, the public key, the first signature, and the common parameters.
3. The device of claim 1, wherein, the device is further configured to compute the second signature as a function of a random number and the private key, wherein the interface receives the random number, and the second signature and the random number are sent via the interface in response to the request, along with the device certificate.
4. The device of claim 1, wherein the application certificate is sent to a server, along with the second signature, the random number, and the device certificate.
5. The device of claim 1, wherein, the device is further configured to create temporary key pairs for applications.
6. The device of claim 1, wherein the on-chip non-volatile memory is read-only memory (ROM) and includes a secret seed random number.
7. The device of claim 1, wherein the certificate generating module is further configured to compute the public key as a function of the private key using an elliptic curve based algorithm.
a means for computing a public key as a function of a private key;
a means for constructing a device certificate as a function of a device ID, an issuer ID, the public key, and a first signature;
a means for receiving a request for the device certificate;
a means for creating a temporary key pair having two keys, a temporary public key and a temporary private key, using a number generator;
a means for creating an application certificate by signing data including the temporary public key, using a stored private key;
a means for using the temporary private key to compute a second signature as a function of a pseudo-random number;
a means for sending the second signature and the pseudo-random number in response to a request, along with the device certificate.
9. The device of claim 8, further comprising a means for computing the public key as a function of the private key and common parameters.
10. The device of claim 8, further comprising a means for constructing the device certificate as a function of the device ID, the issuer ID, the public key, the first signature, and common parameters.
11. The device of claim 8, further comprising a means for computing a second signature as a function of the pseudo-random number and the private key.
12. The device of claim 8, further comprising a means for receiving the pseudo-random number.
13. The device of claim 8, further comprising a means for sending the second signature and the pseudo-random number in response to the request, along with the device certificate.
14. The device of claim 8, further comprising a means for sending the application certificate to a server, along with the second signature, the pseudo-random number, and the device certificate.
15. The device of claim 8, further comprising a means for creating temporary key pairs for applications.
16. The device of claim 8, further comprising a means for computing the public key as a function of the private key using an elliptic curve based algorithm.
using a computer processor:
computing a public key as a function of a private key;
constructing a device certificate as a function of a device ID, an issuer ID, the public key, and a first signature;
receiving a request for the device certificate;
creating a temporary key pair having two keys, a temporary public key and a temporary private key, using a number generator;
creating an application certificate by signing data including the temporary public key, using a stored private key;
using the temporary private key to compute a second signature as a function of a pseudo-random number;
sending the second signature and the pseudo-random number in response to a request, along with the device certificate.
18. The method of claim 17, further comprising computing the public key as a function of the private key and common parameters.
19. The method of claim 17, further comprising constructing the device certificate as a function of the device ID, the issuer ID, the public key, the first signature, and common parameters.
20. The method of claim 17, further comprising computing a second signature as a function of the pseudo-random number and the private key.
21. The method of claim 17, further comprising sending the second signature and the pseudo-random number in response to the request, along with the device certificate.
22. The method of claim 17, further comprising sending the application certificate to a server, along with the second signature, the pseudo-random number, and the device certificate.
23. The method of claim 17, further comprising creating temporary key pairs for applications.
24. The method of claim 17, further comprising computing the public key as a function of the private key using an elliptic curve based algorithm. Description
This application claims priority to U.S. Provisional Patent Application No. 60/857,840, entitled METHOD FOR PROGRAMMING ON-CHIP NON-VOLATILE MEMORY IN A SECURE PROCESSOR, AND A DEVICE SO PROGRAMMED. which was filed Nov. 9, 2006, and which is hereby incorporated in its entirety.
A secure processor typically includes an ID and/or stored secret key. In order to enhance the level of security, the quantities could be programmed in chip-internal non-memory to build a secure processor. The programming of the ID and secret key happen during the secure manufacturing process of the chip. Each ID is unique, and so is the private key. These quantities are used in applications on the device, to implement digital rights management and other security related applications. Typically, the chip includes mechanisms to generate cryptographically strong random numbers to use as nonces in network protocols, secret keys etc.
In a typical infrastructure used for implementing digital rights management, a server is used to supply digitally signed tickets to enable rights for the device. Such tickets use the device identities and/or secret key mechanisms to bind the tickets to the devices. In order to ensure the uniqueness of each device ID/key the server typically uses a secure database to store the IDs, (and/or signed certificates) corresponding to each chip that is manufactured. These certificates contain public keys corresponding to each secret key (private key of a (private, public) key pair) programmed in the chip. In order to populate the database with certificates, the infrastructure associated with the database should be securely coupled with the manufacturing process to maintain a one-to-one correspondence between manufactured chips and certificates in the database.
An improved secure programming technique involves reducing the size of bits programmed in on-chip secret non-volatile memory, at the same time enabling the typical secure applications supported by secure devices. Another improved secure programming technique involves simplifying the process of manufacture of the system. In an embodiment, programming the secrets is isolated to on-chip programming, and, specifically, is isolated from the processes of system integration and infrastructure setup.
A technique for secure programming involves de-coupling chip manufacture from the later process of connecting to ticket servers to obtain tickets. A method according to the technique may involve sending a (manufacturing) server signed certificate from the device prior to any communication to receive tickets. The method may further include populating a database to facilitate performing ticket services later, for example just when the ticket services are needed.
A device according to the technique may include chip-internal non-volatile memory to store the certificate along with the private key, in the manufacturing process. The private key may or may not be an elliptic curve based private key. An advantage of the elliptic curve cryptography based key is that it is smaller than many other types of keys for the relative cryptographic strength. Further, it is possible, using elliptic curve algorithms, to store a random private key and compute the public key by a run-time computation.
Advantageously, especially considering the value of on-chip real estate, a compressed certificate can be provided in the non-volatile memory. Using a smaller data-set (than what would be required to store a device certificate) the device dynamically generates a certificate on the device, to provide to a requesting application. The device certificate may or may not be generated multiple times. For example, the device certificate could be generated once and stored in system external storage for further use. This is not particularly insecure because the certificate is public data.
A device constructed according to the technique may have applicability in other areas. For example, the device could be authenticated to a peer, or to any application that requires a first device certificate. In another alternative, the non-volatile memory may include a secure random number generator for the device, using the secure manufacturing process to program the non-volatile memory.
FIG. 1 depicts an example of a system for validating a client at a server.
FIG. 2 depicts a flowchart of an example of a method for power up and power down of a device appropriate for use in the system.
FIG. 3 depicts a flowchart of an example of a method for generating a device certificate only once.
FIG. 5 depicts an example of a secure system suitable for implementation of the techniques described above with reference to FIGS. 1-3.
FIG. 6 depicts a flowchart of an example of a method for manufacturing a secure device.
FIG. 7 depicts a flowchart of an example of a method for construction of a secure certificate.
FIG. 1 depicts an example of a system 100 for validating a client at a server. In the example of FIG. 1, the system 100 includes a server 102, a network 104, and a client 106. The server 102 includes a certificate request module 110, a certificate verification module 112, a Cert database 114, a pseudo-random number (PRN) generator 116, and an interface 118. The client 106 includes a certificate generation module 120, non-volatile (NV) memory 122, and an interface 124.
The server 102 may be any applicable known or convenient computer. The network 104 may be any communications network including, by way of example but not limitation, the Internet. The client 106 may be any applicable known or convenient computer that has secure storage. The NV memory 122 may include a secure key store and, in an embodiment, the NV memory 122 is on-chip memory.
In the example of FIG. 1, in operation, a protocol for registration or activation is initiated by the server 102. (The client 106 may, in an alternative, initiate the registration or activation.) In an embodiment, the protocol serves to register a device identity and certificate into the cert database 114. To do so, the PRN generator 116 generates a PRN, R, and the certificate request module 110 of the server 102 generates a request for a device certificate. R and the request for a device certificate are sent via the interface 118 to the network 104.
R and the request for a device certificate are received at the interface 124 of the client 106. The certificate generation module 120 of the client 106 generates a certificate Cert. An example of the algorithm used to generate Cert is described with reference to FIG. 7, below. The certificate generation module 120 computes a signature Sig, over random number R, using a device private key. Operands are stored in the NV memory 122, which may reside in, for example, a secure kernel (see e.g., FIG. 5). In an alternative, the computation could include a device ID, serial number, region code, or some other value. The interface 124 of the client 106 returns R, any optional data, Cert, and Sig to the network 104.
The interface 118 receives at the server 102 R, any optional data, Cert, and Sig. The certificate verification module 112 at the server 102 validates Cert using a trusted certificate chain, validates Sig using Cert, and verifies that R is the same as the value, R, that was originally sent by the server 102 to the client 106. If successfully validated and verified, the server 102 imports Cert into the Cert database 116. At this point, the client 106 is presumably authorized to obtain from the server 102—or some other location that can use the certificate to authorize the client 106—digital licenses for rights managed content, and other operations.
In another embodiment, the device could generate a new key pair {pvt1,pub1} using a RNG, and a certificate could be created for the new public key pub1, using the device programmed private key as signer. This new key pvt1 could be used to sign the message having the random R.
It should be noted that secure networking protocols such as SSL and other services that require ephemeral secret keys typically make use of a source of a string of random numbers. A secure manufacturing process, such as is described by way of example but not limitation with reference to FIG. 6, below, can be used to seed a secret random number S in a device. A PRN generating algorithm using cryptographic primitives such as the functions in AES or SHA can be used to generate PRNs. The sequence should not repeat after power-cycle of the device. Using a state-saving mechanism involving the chip non-volatile memory ensures a high level of security. The device uses a part of re-writeable non-volatile memory to store a sequence number.
FIG. 2 depicts a flowchart 200 of an example of a method for power up and power down of a device appropriate for use in the system 100. In the example of FIG. 2, the flowchart 200 starts at module 202 where a device is powered on. In the example of FIG. 2, the flowchart 200 continues to module 204 where runtime state is initialized to 1. Since the runtime state is incremented over time, the runtime state should be stored in writable memory, such as on-chip writable memory.
In the example of FIG. 2, the flowchart 200 continues to module 206 where the device increments the sequence number and computes key=fn(S, sequence number), where S=a programmed secret seed random number. Since S is programmed, it can be stored in on-chip NV read-only memory (ROM). At this point, the device is presumed to be “up and running.”
In the example of FIG. 2, the flowchart 200 continues to module 208 where, in response to a request for a random number, the device generates random=fn(key, state) and increments state: state++. In the example of FIG. 2, the flowchart 200 continues to decision point 210 where it is determined whether another random number request is received. If it is determined that another random number request has been received (210-Y), then the flowchart 200 returns to module 208. In this way, module 208 may be repeated multiple times for multiple random number requests.
When it is determined there are no other random number requests (210-N), the flowchart 200 continues to module 212 where the device is powered off, and the state is lost. Thus, the flowchart 200 illustrates the state of the device from power on to power off. If the device is powered on again, a new key must be computed, and state initialized again.
FIG. 3 depicts a flowchart 300 of an example of a method for generating a device certificate only once. In the example of FIG. 3, the flowchart 300 starts at module 302 where a device certificate is generated at a secure device. The flowchart 300 continues to module 304 where the device certificate is stored in system external storage. This variation is notable because the device is secure, but the device certificate is public. Accordingly, the certificate is still secure, even though it is not regenerated each time.
The computer system 400 may be controlled by an operating system (OS). An OS is a software program—used on most, but not all, computer systems—that manages the hardware and software resources of a computer. Typically, the OS performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking, and managing files. Examples of operating systems for personal computers include Microsoft Windows�, Linux, and Mac OS�. Delineating between the OS and application software is sometimes rather difficult. Fortunately, delineation is not necessary to understand the techniques described herein, since any reasonable delineation should suffice.
FIG. 5 depicts an example of a secure system 500 suitable for implementation of the techniques described above with reference to FIGS. 1-3. A typical secure system 500 may include a game console, media player, an embedded secure device, a “conventional” PC with a secure processor, or some other computer system that includes a secure processor.
In the example of FIG. 5, the secure system 500 includes a secure processor 502, an OS 504, ticket services 506, a calling application 508, and protected memory 510. In the example of FIG. 5, the OS 504 includes a security kernel 514, which in turn includes a key store 516, an encryption/decryption engine 517, and a security API 518. It should be noted that one or more of the described components, or portions thereof, may reside in the protected memory 510, or in unprotected memory (not shown).
It should further be noted that the security kernel 514 is depicted as residing inside the OS 504 by convention only. It may or may not actually be part of the OS 504, and could exist outside of an OS or on a system that does not include an OS. For the purposes of illustrative simplicity, it is assumed that the OS 504 is capable of authentication. In an embodiment, the ticket services 506 may also be part of the OS 504. This may be desirable because loading the ticket services 506 with authentication can improve security. Thus, in such an embodiment, the OS 504 is loaded with authentication and includes the ticket services 506.
For illustrative simplicity, protected memory is represented as a single memory. However protected memory may include protected primary memory, protected secondary memory, and/or secret memory. It is assumed that known or convenient mechanisms are in place to ensure that memory is protected. The interplay between primary and secondary memory and/or volatile and non-volatile storage is known so a distinction between the various types of memory and storage is not drawn with reference to FIG. 5.
The ticket services 506 may be thought of as, for example, “digital license validation services” and, in a non-limiting embodiment, may include known or convenient procedures associated with license validation. For example, the ticket services 506 may include procedures for validating digital licenses, PKI validation procedures, etc. In the example of FIG. 5, the ticket services 506 can validate a ticket from the calling application 508. In operation, the ticket services 506 obtains the ticket from the calling application 508, which proceeds to validate the ticket.
It is possible that the ticket is personalized. In that case, it could be decrypted using the device private key (programmed as discussed before) to compute a secret shared encryption key. The ticket may or may not be obtained using an Internet download mechanism and stored on re-writable flash memory.
In an embodiment, the security kernel 514 may be loaded at start-up. In another embodiment, a portion of the security kernel may be loaded at start-up, and the remainder loaded later. An example of this technique is described in application Ser. No. 10/360,827 entitled “Secure and Backward-Compatible Processor and Secure Software Execution Thereon,” which was filed on Feb. 7, 2003, by Srinivasan et al., and which is incorporated by reference. Any known or convenient technique may be used to load the security kernel 514 in a secure manner.
The key store 516 is a set of storage locations for keys. The key store 516 may be thought of as an array of keys, though the data structure used to store the keys is not critical. Any applicable known or convenient structure may be used to store the keys. In a non-limiting embodiment, the key store 516 is initialized with static keys, but variable keys are not initialized (or are initialized to a value that is not secure). For example, some of the key store locations are pre-filled with trusted values (e.g., a trusted root key) as part of the authenticated loading of the security kernel 514. The private key in the non-volatile memory could be retrieved and stored in the keystore for future use.
The encryption/decryption engine 517 is, in an embodiment, capable of both encryption and decryption. For example, in operation, an application may request of the security API 518 a key handle that the application can use for encryption. The encryption/decryption engine 517 may be used to encrypt data using the key handle. Advantageously, although the security API 518 provides the key handle in the clear, the key itself never leaves the security kernel 514.
The security API 518 is capable of performing operations using the keys in the key store 516 without bringing the keys out into the clear (i.e., the keys do not leave the security kernel 514 or the keys leave the security kernel 514 only when encrypted). The security API 518 may include services to create, populate and use keys (and potentially other security material) in the key store 516. In an embodiment, the security API 518 also provides access to internal secrets and non-volatile data, including secret keys and device private key. For example, the device private key might be stored in the keystore and used by the security API. One API call could be used to return a device certificate (using an algorithm discussed herein to generate the certificate). Another API call can be constructed to use the private key to compute a shared key for decryption, or use the private key to sign a message or certificate. Depending upon the implementation, the security API 518 may support AES and SHA operations using hardware acceleration.
In the example of FIG. 5, the ticket services 506 and the security API 518 may execute in a separate execution space for system security. In order to validate data blocks, the ticket services 506 may validate the ticket using data in the header. The ticket may include an encrypted key. The ticket services 506 decrypts the key using services in the security kernel 514 (e.g., the encryption/decryption engine 517).
In an embodiment, the encryption/decryption engine 517 uses secret common keys from the key store 518 to perform this decryption. In another embodiment, the ticket services 506 could use a device personalized ticket obtained from flash or network (not shown), validate some rights to content, and then return the key. In any case, this process returns the key. The personalized ticket could be encrypted by a key that is a function of the device private key, programmed in the non-volatile memory.
An example of data flow in the system 500 is provided for illustrative purposes as arrows 520-528. Receiving the certificate request at the ticket services 506 is represented by a certificate request arrow 520 from the calling application 508 to the ticket services 506.
Forwarding the certificate request from the ticket services 506 to the security API 516 is represented by a certificate request arrow 522. Within the security kernel 514, the public key/device certificate construction engine 517 accesses keys/signature data from the key/signature store 518. The access is represented by the private key/signature access arrow 524. The security API 516 returns a device certificate to the ticket services 506, as represented by the device certificate arrow 526, which is forwarded to the calling application 508, as represented by the device certificate arrow 528.
FIG. 6 depicts a flowchart 600 of an example of a method for manufacturing a secure device. This method and other methods are depicted as serially arranged modules. However, modules of the methods may be reordered, or arranged for parallel execution as appropriate. In the example of FIG. 6, the flowchart 600 begins at module 602 where a device ID is obtained. The device ID may be a serial number or some other unique identifier for the device.
In the example of FIG. 6, the flowchart 600 continues to module 604 where a pseudo-random number is provided for use as a small-signature private key for the device. To date, truly random numbers are not generable on a computer; of course, a pseudo-random number generator or an external secured hardware true random number generator could work for the intended purpose. A small-signature private key may be, by way of example but not limitation, an elliptic curve private key, or some other private key with a relatively small footprint.
In the example of FIG. 6, the flowchart 600 continues to module 606 where a public key is computed from the private key using common parameters. For example, a multiple of a base point may be computed, where a scalar multiple is the private key.
In the example of FIG. 6, the flowchart 600 continues to module 608 where a fixed certificate structure is used to construct a certificate. The certificate is signed using a small signature algorithm such as elliptic curve DSA. In an embodiment, the fixed certificate structure may include at least the device ID, issuer name, and device public key. A small-signature algorithm is used to minimize the size of the signature. By way of example but not limitation, an elliptic curve signature algorithm may be used.
In the example of FIG. 6, the flowchart 600 continues to module 610 where {device ID, private key, issuer ID, signature} is programmed into the non-volatile memory of the device. This set includes these four items because the items provide sufficient security for most purposes, and the set has a relatively small footprint due to the relatively small size of the private key and signature. (The device ID and issuer ID also, presumably, have relatively small footprints.) In an embodiment, any other data that is needed to construct the device certificate such as the public key may be generated programmatically on demand. However, more items could be programmed into the non-volatile memory, or fewer, as appropriate for a given embodiment or implementation.
In the example of FIG. 6, the flowchart 600 continues to module 612 where a secret random number is programmed into the ROM of the device. The secret random number may be pseudo-randomly generated or arbitrarily assigned. This secret random number can be used to support secure pseudo-random number generation. In an alternative, the ROM may be replaced with some other known or convenient NV storage.
FIG. 7 depicts a flowchart 700 of an example of a method for construction of a secure certificate. Advantageously, the method enables the device having the non-volatile programmed key and required software to construct a full device certificate that can be used to validate the device. In the example of FIG. 7, the flowchart 700 starts at module 702 where a request for a device certificate is received from a calling application.
In the example of FIG. 7, the flowchart 700 continues to module 704 where {device ID, private key, issuer ID, signature} is read from non-volatile memory. In an embodiment, a security kernel module accesses and reads the non-volatile memory. An example of a security kernel module that is appropriate for this purpose is described in U.S. patent application Ser. No. 10/360,827 entitled “Secure and Backward-Compatible Processor and Secure Software Execution Thereon,” which was filed on Feb. 7, 2003, by Srinivasan et al., and/or in U.S. patent application Ser. No. 11/586,446 entitled “Secure Device Authentication System and Method,” which was filed on Oct. 24, 2006, by Srinivasan et al., both of which are incorporated by reference. However, any applicable known or convenient security kernel module could be used.
In the example of FIG. 7, the flowchart 700 continues to module 706 where the public key is computed from the private key and common parameters, if any. In an embodiment, the computation makes use of the same algorithm that was used in a manufacturing process, such as the method described with reference to FIG. 6, above. The public key may be computed in a security kernel.
In the example of FIG. 7, the flowchart 700 continues to module 708 where a device certificate is constructed from device ID, issuer ID, public key, signature, and common parameters. In an embodiment, a security kernel module is aware of the structure of the device certificate, as is used in a manufacturing process, such as the method described with reference to FIG. 6, above. Advantageously, the device certificate can be constructed on demand.
In the example of FIG. 7, the flowchart 700 continues to module 710 where the device certificate is provided to the calling application. The flowchart 700 ends when the device certificate is provided to the calling application. The method could be started again by another calling application (or by the same calling application if, for some reason, the device certificate was needed again.)
As used herein, the term “content” is intended to broadly include any data that can be stored in memory.
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