I am working on ARM-based modem Linux host machine and I need to read a bin file as an 8-,16- or 32- bits array. I basically need to encrypt the file in question and was thinking of just XOR-ing the bits with a random bit sequence (I don't need a very complex system). The Linux host doesn't have C or PERL modules in it so I cannot use them and hence I need to do it using a shell script. Can anyone give me some pointers on how to proceed with this?
Reading a binary file as an array of bytes or 16 or 32 bits using shell script
linux;bash;shell;shell script
Use tr (here rot128):LC_ALL=C tr '\0-\377' '\200-\377\0-\177' < infile > outfileFor XOR 123, you'd need to compute the corresponding tr line:LC_ALL=C tr '\0-\377' '\173\172\171\170\177\176\175\174\163\162\161\160\167\166\165\164\153\152\151\150\157\156\155\154\143\142\141\140\147\146\145\144\133\132\131\130\137\136\135\134\123\122\121\120\127\126\125\124\113\112\111\110\117\116\115\114\103\102\101\100\107\106\105\104\73\72\71\70\77\76\75\74\63\62\61\60\67\66\65\64\53\52\51\50\57\56\55\54\43\42\41\40\47\46\45\44\33\32\31\30\37\36\35\34\23\22\21\20\27\26\25\24\13\12\11\10\17\16\15\14\3\2\1\0\7\6\5\4\373\372\371\370\377\376\375\374\363\362\361\360\367\366\365\364\353\352\351\350\357\356\355\354\343\342\341\340\347\346\345\344\333\332\331\330\337\336\335\334\323\322\321\320\327\326\325\324\313\312\311\310\317\316\315\314\303\302\301\300\307\306\305\304\273\272\271\270\277\276\275\274\263\262\261\260\267\266\265\264\253\252\251\250\257\256\255\254\243\242\241\240\247\246\245\244\233\232\231\230\237\236\235\234\223\222\221\220\227\226\225\224\213\212\211\210\217\216\215\214\203\202\201\200\207\206\205\204'More generally, to answer the question, to convert a file into an array of numbers to be used by the shell with standard commands:set -- $(od -An -vtu1 < infile)You can then apply the transformations you want and convert back to a file with awk's printf(%c).That's going to be very inefficient though.Like:for i in $(od -An -vtu1 < infile); do  echo $(($i ^ 123))done | awk '{printf %c, $0}' > outfileYou can use od -An -vtu2, to get 16bit numbers, but note that it is in the local endianness, so when converting back to characters, you have to take that into account.