Configuration Counting Trade-off - Configuration Counting Trade-off - XAPP1098

Developing Tamper-Resistant Designs with UltraScale and UltraScale+ FPGAs (XAPP1098)

Document ID
XAPP1098
Release Date
2025-05-22
Revision
1.5.1 English

Because there is a fixed amount of overhead associated with each of the individual encrypted blocks, the bitstream size grows larger as the blocks are made increasingly smaller when using the configuration counting random data attack solution. This creates a trade-off that must be considered (configuration storage and time vs. security level). When using key rolling with configuration counting, there is always at least an approximate 14% increase in bitstream size. As the block size decreases (becomes more secure), the bitstream size increases and causes a longer configuration time. The following figure illustrates how bitstream size grows (y-axis) as the as the number of blocks per key are made smaller (x-axis).

Figure 1. Key Rolling With Configuration Counting Trade-off
x1098_05 Sheet.3 X1098_05_082018 X1098_05_082018 Sheet.76 AES Blocks per Key (128 Bits in Each Block) AES Blocks per Key (128 Bits in Each Block) Sheet.98 Sheet.1 Sheet.2 0 0 Sheet.6 Sheet.7 32 32 Sheet.9 Sheet.12 Sheet.14 Sheet.15 Sheet.17 Sheet.18 Sheet.20 Sheet.21 Sheet.23 Sheet.24 Sheet.26 Sheet.27 Sheet.29 Sheet.30 Sheet.32 Sheet.33 Sheet.35 Sheet.36 Sheet.38 Sheet.39 Sheet.41 Sheet.42 Sheet.44 Sheet.45 Sheet.47 Sheet.48 Sheet.50 Sheet.51 Sheet.53 Sheet.54 Sheet.55 Sheet.56 Sheet.57 Sheet.58 Sheet.59 Sheet.60 Sheet.61 Sheet.62 Sheet.63 Sheet.64 Sheet.65 Sheet.66 Sheet.67 Sheet.68 Sheet.69 Sheet.70 Sheet.71 Sheet.72 Sheet.74 Sheet.4 64 64 Sheet.5 96 96 Sheet.8 128 128 Sheet.10 160 160 Sheet.11 192 192 Sheet.13 224 224 Sheet.16 256 256 Sheet.19 288 288 Sheet.22 320 320 Sheet.25 352 352 Sheet.28 384 384 Sheet.31 416 416 Sheet.34 448 448 Sheet.37 480 480 Sheet.40 512 512 Sheet.43 1 1 Sheet.46 1.5 1.5 Sheet.49 2 2 Sheet.52 2.5 2.5 Sheet.75 3 3 Sheet.73 Sheet.77 Sheet.78 Sheet.79 Sheet.80 Sheet.81 Sheet.82 Sheet.83 Sheet.84 Sheet.85 Sheet.86 Sheet.87 Sheet.88 Sheet.89 Sheet.90 Sheet.91 Sheet.92 Sheet.93 Sheet.94 Sheet.95 Sheet.96 Sheet.97 Sheet.99 Bitstream Size/Time Increase Fixed 14% Overhead Bitstream Size/Time Increase Fixed 14% Overhead Sheet.100 Sheet.101 Sheet.102