cryptopals

commit c609e27d8281fe502f7a4d8f394c501daa962944
parent 78ad2edf30c64255edf84e3f8ac6d08cc00b1c6c
Author: Jared Tobin <jared@jtobin.ca>
Date:   Tue,  9 May 2017 23:11:29 +1200

Add 2.1.

Diffstat:
M
README.md
 | 
10
++++++++++
A
lib/pkcs/PKCS.hs
 | 
30
++++++++++++++++++++++++++++++
D
out.txt
 | 
1
-
D
test.out
 | 
0

D
test.txt
 | 
1
-

5 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/README.md b/README.md
@@ -177,3 +177,13 @@ ECB means electronic codebook, the simplest block cipher encryption mode.  One
 divides a message into 16-byte chunks and then encrypts each chunk separately.
 The same 16 bytes will thus encrypt to the same output.
 
+### Set 2
+
+#### 2.1
+
+    $ echo -n 'YELLOW SUBMARINE' | ./bin/pkcs 20 | xxd
+    00000000: 5945 4c4c 4f57 2053 5542 4d41 5249 4e45  YELLOW SUBMARINE
+    00000010: 0404 0404 0a                             .....
+
+
+
diff --git a/lib/pkcs/PKCS.hs b/lib/pkcs/PKCS.hs
@@ -0,0 +1,30 @@
+
+import Control.Error (readMay)
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Char8 as B8
+import GHC.Word
+import System.Environment
+import System.IO
+
+main :: IO ()
+main = do
+  args <- getArgs
+
+  case args of
+    (narg:_) -> case readMay narg :: Maybe Int of
+       Nothing    -> hPutStrLn stderr "pkcs: invalid length"
+       Just padto -> do
+         bytes <- B.getContents
+         let len = B.length bytes
+             npad :: Word8
+             npad = fromIntegral $
+               if   padto < len
+               then 0
+               else padto - len
+
+             padded = B.append bytes (B.replicate (fromIntegral npad) npad)
+         B8.putStrLn padded
+
+    _ -> putStrLn "USAGE: echo STRING | ./pkcs LENGTH"
+
+
diff --git a/out.txt b/out.txt
@@ -1 +0,0 @@
-U2FsdGVkX1/IXdQ+LU0I8umZTye2KKljyOEWcxAjjUf7vUEq9dlBIUZPAwgziT7C
diff --git a/test.out b/test.out
Binary files differ.
diff --git a/test.txt b/test.txt
@@ -1 +0,0 @@
-here's some stuff