Roll back method for a smart card
View Patent ↗In a data carrier ( 2 ) for contactless communication of storage data (SD) with a reader station ( 1 ), a recovery device ( 13 ) is provided, with which, following an unexpected abort of the storing of storage data (SD) in a memory ( 11 ) by virtue of a lack of supply voltage, a valid storage state can be restored in memory ( 11 ). For this purpose, any storage locations that are only weakly stored in memory ( 11 ) will be read, and the read-out storage data (SD) will be re-stored in the memory ( 11 ).
1. A recovery device for recovering valid storage data in a memory, with:
storage means for storing the storage data in storage areas of the memory;
readout means for reading the stored storage data from the storage areas of the memory; and
recovery means for detecting an unexpected abort during the storing of storage data and for recovering valid storage data in the memory, characterized in that the recovery means for recovering valid storage data are designed to re-store the read-out storage data in the same storage area in the memory following the reading of storage data from at least one storage area of the memory;
characterized in that, before the storage of first storage data in a data storage area, the storage means is designed to store second storage data stored in the data storage area in a backup storage area, and that the storage means is designed to store validity information in a validity storage area of memory, wherein first validity information identifies the data storage area, and second validity information identifies the backup storage area as storage areas comprising valid storage data, and that recovery means is designed, before recovering valid storage data in data storage area, to read the validity information, stored in validity storage area, and subsequently to store the read-out validity information in the validity storage area.
2. A recovery means as claimed in claim 1 characterized in that the recovery means is designed to store the first validity information in validity storage area if neither the first nor the second validity information has been read from validity storage area.
3. A recovery means as claimed in claim 1 , characterized in that the storage means is designed to store the first validity information , which is formed, at least at a first bit position, by the bit “ 1 ” and at least at a second bit position, by the bit “ 0 ”, and to store the second validity information, which is formed, at least at the first bit position, by the bit “ 0 ” and at least at a second bit position, by the bit “ 1 ”
4. A recovery means as claimed in claim 3 , characterized in that the recovery means is designed to establish whether the read-out validity information corresponds to the second validity information, and that, in order to store the read-out validity information, the recovery means overstores exclusively bit positions of stored validity information with bits “ 1 ” if the corresponding bit positions of the second validity information established comprise the bit “ 1 ”, wherein a previous erasure procedure is dispensed with during the overstoring of these bit positions.
5. A data carrier for contactless communication with a reader station, with a memory for storing storage data and with communication means for receiving storage data to be stored in the memory and for transmitting storage data read from the memory,
characterized in that a recovery device in accordance with claim 1 is provided.
6. A recovery method, for recovering valid storage data in a memory, wherein the following steps are followed:
storing of storage data in storage areas of the memory;
reading of the stored storage data from the storage areas, of the memory;
detection of an unexpected abort during the storing of storage data
recovery of valid storage data in the memory if an abort has been detected, characterized in that, in order to recover the valid storage data, the read-out storage data is re-stored in the same storage area in the memory following the reading of storage data from at least one storage area of the memory;
characterized in that, before the storing of the first storage data in a data storage area, second storage data stored in data storage area is stored in a backup storage area, and that validity information is stored in a validity storage area of memory, wherein first validity information identifies the data storage area, and second validity information identifies the backup storage area as storage areas comprising valid storage data, and that, before the recovery of valid storage data in data storage area, the validity information stored in validity storage area is read, and subsequently, the read-out validity information is stored in validity storage area.
7. A recovery method as claimed in claim 6 , characterized in that, if neither the first nor the second validity information has been read from validity storage area, the first validity information is stored in validity storage area.
8. A recovery method, as claimed in claim 6 , characterized in that the stored first validity information comprises the bit “ 1 ” at least at a first bit position, and the bit ″ 0 ″ at least at a second bit position, and that the stored second validity information comprises the bit ″ 0 ″ at least at the first bit position, and the bit “ 1 ” at least at the second bit position.
9. A recovery method, as claimed in claim 8 , characterized in that it is established whether the read-out validity information corresponds to the second validity information, and that, in order to store the read-out validity information, exclusively bit positions of the stored validity information are over stored with bits “ 1 ” if the corresponding bit positions of the second validity information established comprise the bit“ 1 ”, wherein, during the overstoring of these bit positions, a previous erasure procedure is dispensed with.