A method for preventing rendering of content at overlapping time periods on more rendering devices (110, 160) than permitted by a license associated with the content, the method comprising: transmitting the following to a rendering device (110, 160) of a user (130, 190): the content; first software; identification information that is associated with the user (130, 190); and second software that comprises a player for rendering the content, where the first software is operative to: generate an asymmetric key pair comprising a public key and a private key; and associate the key pair with the content thus producing a local digital package comprising the content associated with the key pair, the first software, the ID associated with the user (130, 190) and the second software; receiving a pair of number representations X,Y from the rendering device (110, 160) of the user (130, 190) during rendering of the content, where the number representation X comprises a number representation in bits of a result obtained from encrypting together a number representation of a time interval in which an attempt is made to render the content on the rendering device (110, 160) of the user (130, 190) and the ID, both encrypted with the public key of the key pair; and the number representation Y comprises a number representation in bits of a randomly generated share SH of the private key of the key pair, wherein the share SH comprises a portion of the private key such that the private key may be revealed when n+1 shares of the private key are known, but when only n shares of the private key or less than n shares are known, the private key cannot be revealed, where n is a number of rendering devices (110, 160) permitted by the license; receiving additional pairs of number representations X,Y from a plurality of further rendering devices (110, 160) which have received the local digital package from the rendering device (110, 160) of the user (130, 190); detecting an attempt to render the content at overlapping time periods on more rendering devices (110, 160) than permitted by the license associated with the content based on a determination that n+1 different number representations Y are paired with the same number representation X; reconstructing the private key of the key pair, in response to the detecting, by using the shares in the n+1 number representations Y; identifying the ID based on the reconstructed private key; and preventing rendering of the content on all rendering devices (110, 160) associated with the ID. transmitting the following to a rendering device (110, 160) of a user (130, 190): the content; first software; identification information that is associated with the user (130, 190); and second software that comprises a player for rendering the content, where the first software is operative to: generate an asymmetric key pair comprising a public key and a private key; and associate the key pair with the content thus producing a local digital package comprising the content associated with the key pair, the first software, the ID associated with the user (130, 190) and the second software; receiving a pair of number representations X,Y from the rendering device (110, 160) of the user (130, 190) during rendering of the content, where the number representation X comprises a number representation in bits of a result obtained from encrypting together a number representation of a time interval in which an attempt is made to render the content on the rendering device (110, 160) of the user (130, 190) and the ID, both encrypted with the public key of the key pair; and the number representation Y comprises a number representation in bits of a randomly generated share SH of the private key of the key pair, wherein the share SH comprises a portion of the private key such that the private key may be revealed when n+1 shares of the private key are known, but when only n shares of the private key or less than n shares are known, the private key cannot be revealed, where n is a number of rendering devices (110, 160) permitted by the license; receiving additional pairs of number representations X,Y from a plurality of further rendering devices (110, 160) which have received the local digital package from the rendering device (110, 160) of the user (130, 190); detecting an attempt to render the content at overlapping time periods on more rendering devices (110, 160) than permitted by the license associated with the content based on a determination that n+1 different number representations Y are paired with the same number representation X; reconstructing the private key of the key pair, in response to the detecting, by using the shares in the n+1 number representations Y; identifying the ID based on the reconstructed private key; and preventing rendering of the content on all rendering devices (110, 160) associated with the ID.