The following is some information about the SAT attack tool for logic decryption/unlocking described in our paper: Evaluating the Security of Logic Encryption Algorithms, HOST 2015.
The paper itself is available at: http://dl.dropbox.com/u/28673593/web/papers/host15.pdf.
To clone this repository, use the following command.
$ hg clone https://email@example.com/host15author/host15-logic-decryption
This assumes you have the tool mercurial installed. If you do not have mercurial, you can also download a zip file by clicking the download button to the left. The icon for the download button is a cloud with an arrow pointing downwards.
We have provided pre-built binaries for Ubuntu 64-bit Linux. It is suggested that you use these binaries. You can also attempt to build the source in the source/ directory; detailed instructions for this are in COMPILING.md.
The binaries of the decryption and verification tool are stored in the bin/ subdirectory.
The benchmarks are stored in the benchmarks/ subdirectory. There are seven subdirectories in this folder. These are:
The first six subdirectories correspond to the logic encryption schemes evaluated in our paper. For all the schemes except DTC'10/LUT, we provide four encrypted versions for each benchmark. The naming convention for these benchmarks is: <circuit>_enc<PCT>.bench. PCT is a 2 digit number which can be one of 05, 10, 25 and 50 and denotes the percentage area overhead of encryption for this benchmark. For DTC'10/LUT there is only one file for each benchmark and this file is named <circuit>_enc.bench.
The original subdirectory contains the original, unencrypted benchmark circuits.
Running The Decryption Tool
The decryption tool expects two arguments. The first argument is the encrypted benchmark. The second argument is the original benchmark, the latter is only used to evaluate the outputs for distinguishing input patterns.
$ cd bin $ ./sld ../benchmarks/rnd/c880_enc50.bench ../benchmarks/original/c880.bench
The output when this command is run is:
inputs=60 keys=192 outputs=26 gates=590 iteration: 1; vars: 3693; clauses: 4545; decisions: 4318 iteration: 2; vars: 4749; clauses: 7151; decisions: 7160 <many lines snipped> iteration: 47; vars: 52269; clauses: 2120; decisions: 128158 finished solver loop. key=000000110011111011100110110100001001000100000001000010111010001100111111100100001101000010111000010000010011110000111111011001010000001110110011101011111010010100010101110000010110000110000101 iteration=47; backbones_count=0; cube_count=156540; cpu_time=4.42028; maxrss=9.80859
The penultimate output line is the correct key value. The last line is some information about runtime, number of iterations etc.
Verifying Key Values
We have also provided a utility to verify the key value. The program uses a SAT formulation to verify circuit equality. The first argument to this utility is the original unencrypted circuit, the second argument is the encrypted circuit. The third argument must be a string of the form 'key=<keyvalue>'.
An example of its invocation:
$ ./lcmp ../benchmarks/original/c880.bench ../benchmarks/rnd/c880_enc50.bench key=000000110011111011100110110100001001000100000001000010111010001100111111100100001101000010111000010000010011110000111111011001010000001110110011101011111010010100010101110000010110000110000101
The output will be the string 'equivalent' if the correct key is provided. If not, the utility will output the string 'different'. The above command should produce the output 'equivalent'. If any of the key bits are changed, it is very likely that the utility will output 'different'.
Running the Partial-Break Algorithm
In order to run the partial-break algorithm use the -sT flag. To run the fault-analysis attack described in [Rajendran et al., DAC'12], use the -tT flag. To run both the partial-break and fault-analysis attack use the -stT flag. An example:
$ ./sld -stT ../benchmarks/rnd/c880_enc50.bench ../benchmarks/original/c880.bench