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POHow to read first 256 bits from a file to store them in two arrays
 

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  1. POHow to read first 256 bits from a file to store them in two arrays
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    <p>I am coding a cipher, for which key file is 256 bit long. Out of which 128 bits have to go in key and 128 into IV. I am explicitly defining the sizes of those arrays and then reading, and still output I get is Key having like 148 bits set while IV has lesser thus. and in the end it gives stack smashing error.</p> <pre><code>int main(int argc,char *argv[]) { if(argc &lt; 4 || !argv[1] || !argv[2]) { cout &lt;&lt; "Usage: Encoding: " &lt;&lt; argv[0] &lt;&lt; " [plaintext-file] [key-file] [cipher-file]" &lt;&lt; endl; cout &lt;&lt; "Usage: Decoding: " &lt;&lt; argv[0] &lt;&lt; " [cipher-file] [key-file] [plaintext-file]" &lt;&lt; endl; return 0; } unsigned char key[16], iv[16]; unsigned long i; // read input file and size etc FILE* in_file = fopen(argv[1],"rb"); if(!in_file) { cout &lt;&lt; "Error opening read file" &lt;&lt; endl; return 0; } fseek(in_file,0,SEEK_END); unsigned int msglength = ftell(in_file); cout &lt;&lt; "Msglength:" &lt;&lt; msglength &lt;&lt; endl; unsigned char * mem_ptr = (unsigned char*)malloc(msglength); if(!mem_ptr) { cout &lt;&lt; "Error allocating memory" &lt;&lt; endl; fclose(in_file); return 0; } rewind(in_file); fread(mem_ptr,1,msglength,in_file); fclose(in_file); // read keyfile etc FILE* key_file = fopen(argv[2],"rb"); if(!key_file) { cout &lt;&lt; "Error opening key file" &lt;&lt; endl; return 0; } fseek(key_file,0,SEEK_END); unsigned int key_size = ftell(key_file); cout &lt;&lt; "Key Size:" &lt;&lt; key_size &lt;&lt; endl; unsigned char * key_ptr = (unsigned char*)malloc(key_size); if(!key_ptr) { cout &lt;&lt; "Error allocating memory" &lt;&lt; endl; fclose(key_file); return 0; } rewind(key_file); fread(key_ptr,1,key_size,key_file); cout &lt;&lt; "sizeof key"&lt;&lt;sizeof(key)&lt;&lt;" sizeof iv" &lt;&lt; sizeof(iv) &lt;&lt; endl; for (i=0; i&lt;256; i++) { if (i&lt;128) key[i] = key_ptr[i]; else iv[i-128] = key_ptr[i]; } cout &lt;&lt; key_ptr &lt;&lt; endl; cout &lt;&lt; "Key:" &lt;&lt; key &lt;&lt; endl &lt;&lt; "IV:" &lt;&lt; iv &lt;&lt; endl; } </code></pre> <p>Output</p> <pre><code>Msglength:15 Key Size:257 sizeof key16 sizeof iv16 abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678 Key:abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678 IV:abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678 *** stack smashing detected ***: ./a.out terminated Segmentation fault (core dumped) </code></pre> <p>Any idea where am I going wrong?</p>
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    1. COi changed declaration to key[128] etc, and initialized to 0 and the stack smashing is gone, however the key and IV aren't still the same length
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      1. POHow to read first 256 bits from a file to store them in two arrays
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