set6: task41: SOLVED!

1 files changed, 55 insertions, 0 deletions

diff --git a/set6/task41.c b/set6/task41.c
new file mode 100644
index 0000000..6793ecc
--- /dev/null
+++ b/set6/task41.c
@@ -0,0 +1,55 @@
+#include "../lib/lib.h"
+#include "../lib/lib2.h"
+#include "../lib/lib3.h"
+#include "../lib/lib4.h"
+#include "../lib/lib5.h"
+#include "../lib/lib6.h"
+
+int main()
+{
+	struct rsa_key_bignum public, private;
+	unsigned char *mess = "Love of my live you hurt me. You stolen my heart";
+	BIGNUM *bn_mess = BN_bin2bn(mess, strlen(mess), NULL);
+	BIGNUM *encrypted = BN_new();
+	BIGNUM *decrypted = BN_new();
+	out = BIO_new(BIO_s_file());
+	BIO_set_fp(out, stdout, BIO_NOCLOSE);
+	ctx = BN_CTX_new();
+
+	printf("plaintext is: %s\n", mess);
+	BN_print(out, bn_mess);
+
+	rsa_generate_key_bignum(&public, &private);
+
+	rsa_encrypt_bignum(bn_mess, encrypted, &public);
+
+	printf("\nencrpyted message is:\n");
+	BN_print(out, encrypted);
+	BIGNUM *S = BN_new();
+	// genrate random value mod N
+	BN_pseudo_rand(S, 256, -1, -1);
+	BN_nnmod(S, S, public.modulo, ctx);
+	
+	BIGNUM *C_ = BN_new();
+	BIGNUM *tmp = BN_new();
+
+	BN_mod_exp(tmp, S, public.exponent, public.modulo, ctx);
+	BN_mod_mul(C_, tmp, encrypted, public.modulo, ctx);
+
+	printf("\nmodified ciphertext for decryption is:\n");
+	BN_print(out, C_);
+
+	// ok submit this totally differen ciphertext for decryption
+	rsa_decrypt_bignum(C_, decrypted, &private);
+	// multiply by modinv of s
+	modular_multiplicative_inverse_bignum_my(tmp, S, public.modulo);
+	BN_mod_mul(tmp, decrypted, tmp, public.modulo, ctx);
+	printf("\nrecovered plaintext is:\n");
+	BN_print(out, tmp);
+	printf("\n");
+	unsigned char *__dec = malloc(strlen(mess));
+	memset(__dec, 0, strlen(mess));
+	BN_bn2bin(tmp, __dec);
+	printf("recovered plaintext: %s\n", __dec);
+
+}