add a funny #ifdef RNG_XKCD that grounds the RNG

diff --git a/d0_blind_id.c b/d0_blind_id.c
index 44bcaf82990b08cc4e655a607803df7a860af930..a7a1c9679c45665bde08fa408e14e05066fa930a 100644 (file)
--- a/d0_blind_id.c
+++ b/d0_blind_id.c
@@ -765,12 +765,19 @@ D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_start(d0_
        // start schnorr ID scheme
        // generate random number r; x = g^r; send hash of x, remember r, forget x
        CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
+#ifdef RNG_XKCD
+       CHECK_ASSIGN(ctx->r, d0_bignum_int(ctx->r, 4)); // decided by fair dice roll
+#else
        CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
-       //CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
+#endif
 
        // initialize Signed Diffie Hellmann
        // we already have the group order in temp1
+#ifdef RNG_XKCD
+       CHECK_ASSIGN(ctx->t, d0_bignum_int(ctx->t, 4)); // decided by fair dice roll
+#else
        CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
+#endif
        // can we SOMEHOW do this with just one mod_pow?
 
        CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
@@ -869,12 +876,20 @@ D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_challenge
        CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
 
        // send challenge
+#ifdef RNG_XKCD
+       CHECK_ASSIGN(ctx->challenge, d0_bignum_int(ctx->challenge, 4)); // decided by fair dice roll
+#else
        CHECK_ASSIGN(ctx->challenge, d0_bignum_rand_bit_atmost(ctx->challenge, SCHNORR_BITS));
+#endif
        CHECK(d0_iobuf_write_bignum(out, ctx->challenge));
 
        // Diffie Hellmann send
        CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
+#ifdef RNG_XKCD
+       CHECK_ASSIGN(ctx->t, d0_bignum_int(ctx->t, 4)); // decided by fair dice roll
+#else
        CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
+#endif
        CHECK(d0_bignum_mod_pow(temp0, four, ctx->t, ctx->schnorr_G));
        CHECK(d0_iobuf_write_bignum(out, temp0));