From 4e0e29f48f797206a21aa5ba7855ffde72e85cf9 Mon Sep 17 00:00:00 2001
From: Benedict <benedict@0xb8000.de>
Date: Thu, 4 Aug 2016 19:24:17 +0200
Subject: completed set3, challenge 20

---
 lib/lib.c  | 27 +++++++++++++++++++++++++++
 lib/lib.h  |  2 +-
 lib/lib2.c | 10 +++++++---
 lib/lib2.h |  1 +
 4 files changed, 36 insertions(+), 4 deletions(-)

(limited to 'lib')

diff --git a/lib/lib.c b/lib/lib.c
index 7c8beae..0e02726 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -555,4 +555,31 @@ int string_is_ecb_encrypted(char *string, int length_string, int blocksize)
 	return (count_equal_blocks(string, length_string, blocksize) > (length_string/blocksize));
 }
 
+/**
+* split ciphertext in blocks of size blocksize
+ * @return returns an array of string of size with blocksize elements
+ */
+
+
+char **transpose_blocks(char *ciphertext, int blocksize, int length)
+{
+	char **blocks;
+	int i, j;
+	int number_blocks = length / blocksize;
+
+	blocks = malloc(blocksize*(sizeof(char*)));
+
+	for(i=0;i<blocksize;i++) {
+		blocks[i] = malloc(number_blocks+1);
+	}
+
+	for(j=0;j<blocksize;j++) {
+		for(i=0;i<number_blocks;i++) {
+			blocks[j][i] = ciphertext[(i*blocksize)+j];
+		}
+	}
+
+	return blocks;
+}
+
 
diff --git a/lib/lib.h b/lib/lib.h
index 8e384e8..a561442 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -24,6 +24,6 @@ char brute_force_single_byte_xor(char *string, int length, struct key_and_freq *
 int isprintable(char *string, int length);
 int read_base64_file(const char *file, char **out);
 int string_is_ecb_encrypted(char *string, int length_string, int blocksize);
-
+char **transpose_blocks(char *ciphertext, int blocksize, int length);
 
 #endif /* __CYRPTO_LIB__ */
diff --git a/lib/lib2.c b/lib/lib2.c
index c7e6ebb..e447054 100644
--- a/lib/lib2.c
+++ b/lib/lib2.c
@@ -6,12 +6,11 @@
  * and append to last block so that it is also of blocksize length
  */
 
-char *pkcs7_padding(char *string, int length_string, int blocksize)
+char *__pkcs7_padding(char *string, int length_string, int blocksize, int *padding)
 {
 	char *result = NULL;
 	int i;
 	int value = blocksize - (length_string % blocksize);
-
 	result = malloc(length_string+value+1);
 	memcpy(result, string, length_string);
 
@@ -19,10 +18,15 @@ char *pkcs7_padding(char *string, int length_string, int blocksize)
 		result[length_string+i] = (char) value;
 	}
 	result[length_string+i] = '\0';
-
+	*padding = value;
 	return result;
 }
 
+char *pkcs7_padding(char *string, int length_string, int blocksize)
+{
+	int not_interested;
+	return __pkcs7_padding(string, length_string, blocksize, &not_interested);
+}
 /**
  * unpadd a string
  * @param in string which should be unpadded
diff --git a/lib/lib2.h b/lib/lib2.h
index f0a1a26..e5666ea 100644
--- a/lib/lib2.h
+++ b/lib/lib2.h
@@ -15,6 +15,7 @@ char key[17];
 char iv[17];
 
 char *pkcs7_padding(char *string, int length_string, int blocksize);
+char *__pkcs7_padding(char *string, int length_string, int blocksize, int *padding);
 int aes_cbc(char *in, int length_in, char *out, unsigned char *string_key, char *init_vector, int encrypt);
 int valid_pkcs7_padding(const char *in, int length_in, char *unpadded, int blocksize);
 int aes_ecb(char *in, int length_in, char *out, unsigned char *string_key,
-- 
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