Patents by Inventor Per Stahl

Per Stahl has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20100299748
    Abstract: The invention relates to a method for enabling modifications of integrity protected data, such as SIM lock settings, in a device. The method comprises: in a device, creating a data entity containing signed change information about allowable alterations, the change information being bound to the device, a certificate with a public key corresponding to the private key used to sign the change information; accessing the device and requesting alteration; verifying the requested alteration against the data entity; and if the verification succeeds, performing the requested alteration. By centrally preparing dedicated replacement devices, which locally can be altered in a simple and secure way, without compromising sensitive information or data, a more secure handling of alteration is achieved. Also, the invention relates to a corresponding computer program product and a device implementing the method.
    Type: Application
    Filed: November 27, 2008
    Publication date: November 25, 2010
    Applicant: TELEFONAKTIEBOLAGET L M ERICSSON (PUBL)
    Inventors: Mikael Johansson, Per Stahl
  • Publication number: 20100180130
    Abstract: An electronic device requires valid control keys to change any usage restriction setting. The device is provided control keys, a secret key, and a signed software object including a batch ID and a hash of the secret key. For each control key, the device generates a cryptographic footprint bound to the device and the secret key. A message authentication code (MAC) of each usage restriction setting is generated, the MAC bound to the device and a control key. To change a usage restriction, the device receives a control key, validates it against the stored footprint, changes the usage restriction settings, and generates a new usage restriction setting MAC. The control key footprints are bound to the secret key, but the device retains only a hash of the secret key.
    Type: Application
    Filed: January 9, 2009
    Publication date: July 15, 2010
    Applicant: Telefonaktiebolaget LM Ericsson (publ)
    Inventors: Per Stahl, Chris Loreskar, Bernard Smeets
  • Publication number: 20090313471
    Abstract: Disclosed is a method and a system for rendering content on external devices securely. The method comprises setting up a communication channel between a proxy rendering server of a mobile device and an external rendering server of an external device, authenticating at least the external rendering server and upon successful authentication transferring a key from the proxy rendering server to the external rendering server, transferring the content encrypted with the transferred key from the proxy rendering server to the external rendering server for rendering the content, wherein the rendering of the content is performed in one of two modes, either in a preprocessing mode or in a non-preprocessing mode, and wherein a DRM agent is only present in the mobile device.
    Type: Application
    Filed: May 8, 2007
    Publication date: December 17, 2009
    Inventors: Ulf Björkengren, Per Stáhl, Magnus L. Olsson
  • Patent number: 7617158
    Abstract: Digital rights management is described involving a device, a content issuer, and a rights issuer. A content encryption key (CEK) is encrypted using a public key associated with the device to produce an encrypted CEK. The encrypted CEK is encrypted using an issuer encryption key to produce a twice encrypted CEK. The twice encrypted CEK is encrypted using the public key to produce a ciphertext included in a rights object. The rights object is available to the device for decrypting digital content associated with the content issuer. The device can then decrypt the rights object ciphertext using its private key to produce a decrypted rights object ciphertext and decrypt the decrypted rights object ciphertext using an issuer decryption key received from the content issuer to produce an encrypted CEK. The encrypted CEK is decrypted using the private key to obtain the CEK, which is then available for decrypting digital content.
    Type: Grant
    Filed: August 26, 2004
    Date of Patent: November 10, 2009
    Assignee: Telefonaktiebolaget L M Ericsson (publ)
    Inventors: Ulf Björkengren, Per Ståhl
  • Publication number: 20090164800
    Abstract: Methods and apparatus for verifying that an electronic device has been disabled are disclosed. An exemplary electronic device includes a communications interface, a secure memory, storing a secret key, and a cryptographic circuit configured to calculate a verification token from the secret key, using a first cryptographic operation. The cryptographic circuit is further configured to calculate an identification token from the verification token, using a second cryptographic operation. The cryptographic circuit is further configured to output the identification token in response to a first command received via the communications interface. The verification token is output to the communications interface only if a predetermined functionality of the electronic device has been disabled. The electronic device may further comprise a disabling circuit configured to disable the predetermined functionality in response to a disable command.
    Type: Application
    Filed: December 21, 2007
    Publication date: June 25, 2009
    Inventors: Petri Mikael Johansson, Per Stahl
  • Publication number: 20050209972
    Abstract: Digital rights management is described involving a device, a content issuer, and a rights issuer. A content encryption key (CEK) is encrypted using a public key associated with the device to produce an encrypted CEK. The encrypted CEK is encrypted using an issuer encryption key to produce a twice encrypted CEK. The twice encrypted CEK is encrypted using the public key to produce a ciphertext included in a rights object. The rights object is available to the device for decrypting digital content associated with the content issuer. The device can then decrypt the rights object ciphertext using its private key to produce a decrypted rights object ciphertext and decrypt the decrypted rights object ciphertext using an issuer decryption key received from the content issuer to produce an encrypted CEK. The encrypted CEK is decrypted using the private key to obtain the CEK, which is then available for decrypting digital content.
    Type: Application
    Filed: August 26, 2004
    Publication date: September 22, 2005
    Inventors: Ulf Bjorkengren, Per Stahl
  • Publication number: 20050087186
    Abstract: A system for heating liquid using solar radiation, includes a plurality of solar panels (1, 2, 3, 4, 5), at least one reservoir for heated liquid and pipes for circulating liquid between the respective solar panel and the at least one liquid reservoir, the liquid circulating by gravity circulation. The present system is characterised in that a non-return valve (17) for controlling the flow of heated liquid from the respective solar panel is placed in a portion of the circulation pipe between the upper end of the solar panel and the at least one liquid reservoir, the non-return valve (17) being adapted to open and close at a predetermined pressure in the liquid flow from the solar panel.
    Type: Application
    Filed: October 20, 2004
    Publication date: April 28, 2005
    Inventor: Per Stahl
  • Patent number: 5468650
    Abstract: A histamine diagnostic assay device is provided in which glass microfibers treated with a polar organic polymer are deposited onto a carrier and used to selectively bind histamine in a sample. The polar organic polymer reduces the affinity of the glass microfibers for interfering components of the sample while substantially retaining the histamine-binding capacity. Preferably, the glass microfibers are provided as a conglomerate with the polar organic polymer. An agent which induces the release of histamine from cells in the sample may be included in the device.
    Type: Grant
    Filed: February 28, 1994
    Date of Patent: November 21, 1995
    Assignee: A/S Lundbeck Export Division Ltd.
    Inventors: Per Stahl Skov, Ole-Christian Bjarno
  • Patent number: 5098831
    Abstract: The histamine in a sample is determined by contacting the sample with a histamine binding agent, such as glass, which has been treated, e.g., with a polar organic polymer, to reduce the affinity of the agent for an interfering component of the sample while substantially retaining the agent's histamine-binding capacity. Such an agent facilitates determination of histamine in whole blood samples. Preferably, the agent is provided as a conglomerate of histamine-binding bodies, such as glass fibers, in a binder. Preferred binders are polyvinyl acetate, a vinyl acetate/ethylene copolymer, and polyvinyl alcohol or combinations thereof.
    Type: Grant
    Filed: August 10, 1989
    Date of Patent: March 24, 1992
    Assignee: Allergifonden af 1981
    Inventors: Per Stahl Skov, Ole-Christian Bjarno