Extraction of video streams

A non-transitory computer-readable storage medium, storing a computer program comprising program instructions, the computer program able to be loaded into a data processing unit and adapted for causing the data processing unit to implement a method for selective extraction, by a terminal, of at least one image to be extracted contained in an encrypted video stream,

• wherein multiple encrypted versions of said encrypted video stream are stored on a server incapable of decrypting said encrypted versions of the video stream,
• said multiple encrypted versions comprising at least a low resolution version and a high resolution version,
• each encrypted version of said encrypted video stream being divided into encrypted blocks, each encrypted block containing multiple encrypted images, said method comprising:
• selecting of an encrypted block of the low resolution encrypted version of the encrypted video stream, said encrypted block containing an image to be extracted;
• selecting of a subset of said encrypted block containing said image to be extracted, wherein the subset starts at a beginning of the encrypted block and has a size strictly greater than the size of the image to be extracted;
• transmitting, by the server to the terminal, of said subset;
• decryption of said subset by the terminal;
• extracting, by the terminal, of said image to be extracted, from said decrypted subset.

A terminal arranged for selective extraction of at least one image to be extracted contained in an encrypted video stream, wherein

• multiple encrypted versions of said encrypted video stream being stored on a server incapable of decrypting said encrypted versions of the video stream,
• said multiple encrypted versions of said encrypted video stream comprising at least a low resolution version and a high resolution version,
• each encrypted version of said encrypted video stream being divided into encrypted blocks, each encrypted block containing multiple encrypted images, said terminal comprising:
• an electronic circuit for selecting an encrypted block of the low resolution encrypted version of the video stream, said encrypted block containing at least one image to be extracted;
• an electronic circuit for selecting a subset of said encrypted block containing said image to be extracted, wherein the subset starts at a beginning of the encrypted block and has a size strictly greater than the size of the image to be extracted;
• an electronic circuit for receiving said subset from the server;
• an electronic circuit for decrypting said subset;
• an electronic circuit for extracting said image to be extracted from said decrypted subset.

A server arranged for storing multiple encrypted versions of an encrypted video stream, said server not being able to decrypt said encrypted versions of said encrypted video stream,

• said multiple encrypted versions of said encrypted video stream comprising at least a low resolution version and a high resolution version,
• each encrypted version of the video stream being divided into encrypted blocks, each encrypted block containing multiple encrypted images, said server comprising:
• an electronic circuit for selecting an encrypted block from the low resolution encrypted version of the encrypted video stream, said encrypted block containing an image to be extracted;
• an electronic circuit for selecting a subset of said encrypted block containing said image to be extracted, wherein the subset starts at a beginning of the encrypted block and has a size strictly greater than the size of the image to be extracted;
• an electronic circuit for transmitting said subset to a terminal.