From 29591502e2ab22a262063e5552438b23380b3e55 Mon Sep 17 00:00:00 2001
From: Benedict <benedict@0xb8000.de>
Date: Sat, 17 Dec 2016 17:40:31 +0100
Subject: set6: challenge 43: completed

---
 set6/task43.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 set6/task43.c

(limited to 'set6')

diff --git a/set6/task43.c b/set6/task43.c
new file mode 100644
index 0000000..b1386fa
--- /dev/null
+++ b/set6/task43.c
@@ -0,0 +1,98 @@
+#include "../lib/lib.h"
+#include "../lib/lib2.h"
+#include "../lib/lib3.h"
+#include "../lib/lib4.h"
+#include "../lib/lib5.h"
+#include "../lib/lib6.h"
+#include <openssl/sha.h>
+
+int main()
+{
+	int i;
+	struct dsa_public_params dsa_pub;
+	struct dsa_per_user_param dsa_user;
+	struct dsa_per_user_param dsa_user_org;
+	BIGNUM *hash_bn = BN_new();
+	BIGNUM *k = BN_new();
+	char *message = "For those that envy a MC it can be hazardous to your health\nSo be friendly, a matter of life and death, just like a etch-a-sketch\n";
+	
+	out = BIO_new(BIO_s_file());
+	BIO_set_fp(out, stdout, BIO_NOCLOSE);
+	ctx = BN_CTX_new();
+
+	printf("message is:\n%s\n", message);
+	SHA_CTX sha1;
+	char sha1_hash[20];
+	char hex[40];
+	dsa_user.public = BN_new();
+	dsa_user.private = BN_new();
+	dsa_user.r= BN_new();
+	dsa_user.s = BN_new();
+
+	dsa_user_org.public = BN_new();
+	dsa_user_org.private = BN_new();
+	dsa_user_org.r= BN_new();
+	dsa_user_org.s = BN_new();
+
+	SHA1_Init(&sha1);
+	SHA1_Update(&sha1, message, strlen(message));
+	SHA1_Final(sha1_hash, &sha1);
+	hex_binary_to_string(sha1_hash, hex, 20);
+	printf("hash of message is: %s\n", hex);
+	BN_bin2bn(sha1_hash, 20, hash_bn);
+	BN_print(out, hash_bn);
+
+	init_dsa_pub_param(&dsa_pub);
+
+	// set public key
+	char *  y = "84ad4719d044495496a3201c8ff484feb45b962e7302e56a392aee4"
+	"abab3e4bdebf2955b4736012f21a08084056b19bcd7fee56048e004"
+	"e44984e2f411788efdc837a0d2e5abb7b555039fd243ac01f0fb2ed"
+	"1dec568280ce678e931868d23eb095fde9d3779191b8c0299d6e07b"
+	"bb283e6633451e535c45513b2d33c99ea17";
+	char *r = "548099063082341131477253921760299949438196259240";
+	char *s = "857042759984254168557880549501802188789837994940";
+
+	BN_hex2bn(&dsa_user.public, y);
+	// well this is decimal ....
+	BN_dec2bn(&dsa_user.r, r);
+	BN_dec2bn(&dsa_user.s, s);
+
+	BN_copy(dsa_user_org.public, dsa_user.public);
+	BN_copy(dsa_user_org.r, dsa_user.r);
+	BN_copy(dsa_user_org.s, dsa_user.s);
+
+	// can i verfiy that?
+	// brute force
+	BIGNUM *tmp = BN_new();
+	for(i=0;i<65536;i++) {
+		BN_set_word(k, i);
+		//BN_copy(dsa_user.r, dsa_user_org.r);
+		//BN_copy(dsa_user.s, dsa_user_org.s);
+		//BN_copy(dsa_user.public, dsa_user_org.public);
+		dsa_recover_x_from_known_k(&dsa_pub, k, &dsa_user, hash_bn);
+		// compute signture with this x,k and compare
+		printf("\nprivate key for k = %i\n", i);
+		BN_print(out, dsa_user.private);
+		//dsa_sign(message, &dsa_pub, &dsa_user, k);	
+		BN_mod_exp(tmp, dsa_pub.g, dsa_user.private, dsa_pub.p, ctx);
+		if(!BN_cmp(tmp, dsa_user.public))
+			break;
+	}
+	printf("\nk is: %i, private key:\n", i);
+	BN_print(out, dsa_user.private);
+	char *str_priv = malloc(BN_num_bytes(dsa_user.private));
+	char *str_priv_hex = malloc(BN_num_bytes(dsa_user.private)*2+1);
+	BN_bn2bin(dsa_user.private, str_priv);
+	hex_binary_to_string(str_priv, str_priv_hex, BN_num_bytes(dsa_user.private));
+
+	SHA1_Init(&sha1);
+	SHA1_Update(&sha1, str_priv_hex, BN_num_bytes(dsa_user.private)*2);
+	SHA1_Final(sha1_hash, &sha1);
+
+	char *given_hash = "0954edd5e0afe5542a4adf012611a91912a3ec16";
+	hex_binary_to_string(sha1_hash, hex, 20);
+	printf("\nhash of private key is: %s\n", hex);
+	printf("given one: %s\n", given_hash);
+	printf("equal?: %i", !memcmp(hex, given_hash, 20));
+}
-- 
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