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Registered: ‎12-02-2012

Loading unencrypted bitstreams onto encrypted FPGA

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I don't think this was ever explicitly mentioned in the docs (or if it was I didn't find it when perusing), but if I have an FPGA with either the efuse or the bbram programmed with an encryption key, is it still able to load unencrypted bitstreams, or must any bitstream it attempts to load be encrypted with the appropriate key?

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Registered: ‎01-22-2015

Re: Loading unencrypted bitstreams onto encrypted FPGA

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@zwabbit 

For 7-series devices, the warnings in and around Table 5-17 of UG470 indicate that when eFUSE bit-0 is programmed then you can only load encrypted bitstreams to the FPGA.  -and unfortunately there is no way to undo this.

However, if the battery-backed-SRAM (BBRAM) is being used instead of eFUSE with bitstream encryption, then you can undo things.  That is, if you remove power, VCCBATT, from the BBRAM and cycle power to the FPGA then you can again load unencrypted bitstreams.

Mark

 

 

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174 Views
Registered: ‎01-22-2015

Re: Loading unencrypted bitstreams onto encrypted FPGA

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@zwabbit 

For 7-series devices, the warnings in and around Table 5-17 of UG470 indicate that when eFUSE bit-0 is programmed then you can only load encrypted bitstreams to the FPGA.  -and unfortunately there is no way to undo this.

However, if the battery-backed-SRAM (BBRAM) is being used instead of eFUSE with bitstream encryption, then you can undo things.  That is, if you remove power, VCCBATT, from the BBRAM and cycle power to the FPGA then you can again load unencrypted bitstreams.

Mark

 

 

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