cryptopals

commit 78ad2edf30c64255edf84e3f8ac6d08cc00b1c6c
parent 9867f7afe672e61231cc105469e38c63fbffecea
Author: Jared Tobin <jared@jtobin.ca>
Date:   Mon,  8 May 2017 10:29:31 +1200

Polish off set 1.

Diffstat:
M
README.md
 | 
17
++++++++++++++++-
M
lib/chunks/Chunks.hs
 | 
9
++++++---

2 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/README.md b/README.md
@@ -153,7 +153,7 @@ Shift by 32 for readability:
 
 #### 1.7
 
-I use openssl less than I code, heck the rules:
+I like openssl, heck the rules:
 
     $ KEY=$(echo -n 'YELLOW SUBMARINE' | xxd -p)
     $ openssl enc -aes-128-ecb \
@@ -162,3 +162,18 @@ I use openssl less than I code, heck the rules:
     I'm back and I'm ringin' the bell
     A rockin' on the mike while the fly girls yell
 
+#### 1.8
+
+    $ cat data/s1/q8_input.txt | parallel \
+        'echo -n {} | ./bin/chunks 8 | printf "%.10s %u\n" {} \
+          $(datamash countunique 1)' | awk '{ if ($2 < 20) { print }; }'
+    d880619740 14
+
+So, the line starting with 'd880619740' - line 133.
+
+**Background**:
+
+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.
+
diff --git a/lib/chunks/Chunks.hs b/lib/chunks/Chunks.hs
@@ -5,6 +5,7 @@
 import Control.Error (readMay)
 import qualified Data.ByteString as B
 import qualified Data.ByteString.Char8 as B8
+import qualified Data.ByteString.Base16 as B16
 import System.Environment
 import System.IO
 
@@ -24,8 +25,10 @@ main = do
     (narg:_) -> case readMay narg :: Maybe Int of
        Nothing   -> hPutStrLn stderr "chunks: invalid keysize"
        Just size -> do
-         bs <- B8.getContents
-         let chunked = chunks size (B8.filter (/= '\n') bs)
-         mapM_ B8.putStrLn chunked
+         hex <- B.getContents
+         let (bs, _) = B16.decode hex
+             chunked = chunks size bs
+             rehexed = fmap B16.encode chunked
+         mapM_ B8.putStrLn rehexed
 
     _ -> putStrLn "USAGE: echo FOO | ./chunks KEYSIZE"