Program apps/garbled/examples/hmac-sha256.mpcl

This example computes HMAC-SHA256 where the HMAC key is shared as two random shares between garbler and evaluator. The garbler's key share is:

keyG: 4de216d2fdc9301e5b9c78486f7109a05670d200d9e2f275ec0aad08ec42af47
      fcb59bf460d50b01333a748f3a9efb13e08036d49a26c21ba2e33a5f8a2cf0e7

The evaluator's key share is:

keyE: f87a00ef89c2396de32f6ac0748f6fa1b641013d46f74ce25cc625904215a675
      01c0c7196a2602f6516527958a82271847933c35d170d98bfdb04d2ddf3bb197

The final HMAC key is keyG ^ keyE:

key : b598163d740b0973b8b312881bfe6601e031d33d9f15be97b0cc8898ae570932
      fd755ced0af309f7625f531ab01cdc0ba7130ae14b561b905f53777255174170

The example uses 32-byte messages (Garbler.msg) so with the message:

msg : Hello, world!...................
hex : 48656c6c6f2c20776f726c64212e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e

We expect to get the following HMAC-SHA256 output:

sum : 60d27dbd14f1e351f20069171fead00ef557d17ac9a41d02baa488ca4b90171a

Now we can run the MPC computation as follows. First, run the evaluator with one input: the evaluator's key share:

./garbled -e -v -i 0xf87a00ef89c2396de32f6ac0748f6fa1b641013d46f74ce25cc625904215a67501c0c7196a2602f6516527958a82271847933c35d170d98bfdb04d2ddf3bb197 examples/hmac-sha256.mpcl

The garbler takes two inputs: the message and the garbler's key share:

./garbled -v -i 0x48656c6c6f2c20776f726c64212e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e,0x4de216d2fdc9301e5b9c78486f7109a05670d200d9e2f275ec0aad08ec42af47fcb59bf460d50b01333a748f3a9efb13e08036d49a26c21ba2e33a5f8a2cf0e7 examples/hmac-sha256.mpcl

The MCP computation providers the expected HMAC result:

Result[0]: 60d27dbd14f1e351f20069171fead00ef557d17ac9a41d02baa488ca4b90171a