commit 4dfd78fc3a1797b463ab4b5441a2a9ffd56fef0c
parent 19ba71dee41a230fbff2ae60f829528e4a3dfd83
Author: Jared Tobin <jared@jtobin.ca>
Date: Sun, 7 May 2017 16:29:53 +1200
Update notes.
Diffstat:
| M | README.md | | | 55 | +++++++++++++++++++++++++++++++++++++++++++++++++++---- |
1 file changed, 51 insertions(+), 4 deletions(-)
diff --git a/README.md b/README.md
@@ -21,11 +21,25 @@ This is illustrated for 1.1.
$ SOLUTION=$(cat data/s1/q1_input.txt | ./bin/hex2b64)
$ diff <(echo $SOLUTION) data/s1/q1_output.txt
+One could write no code at all:
+
+ $ xxd -r -p data/s1/q1_input.txt | base64
+
+It's also fun to check the ASCII-encoded input:
+
+ $ xxd -r -p data/s1/q1_input.txt
+ I'm killing your brain like a poisonous mushroom
+
#### 1.2
- $ ./bin/fixed_xor $(< data/s1/q2_input.txt) $(< data/s1/q2_against.txt)
+ $ SOLUTION=$(./bin/fixed_xor $(< data/s1/q2_input.txt) $(< data/s1/q2_against.txt))
746865206b696420646f6e277420706c6179
+ASCII-encoded output is fun:
+
+ $ echo $SOLUTION | xxd -r -p
+ the kid don't play
+
#### 1.3
$ ./bin/charfreq $(< data/s1/q3_input.txt)
@@ -44,10 +58,23 @@ This is illustrated for 1.1.
xored with: 120 (x)
decrypted: cOOKINGmcSLIKEAPOUNDOFBACON
+Here it's worth noting that you can usually get a better decryption by using
+the opposite case, so (ASCII-encoded +- 32):
+
+ $ cat data/s1/q3_input.txt | ./bin/single_byte_xor 88
+ original: 1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736
+
+ xored with: 88 (X)
+ decrypted: Cooking MC's like a pound of bacon
+
#### 1.4
$ parallel -a data/s1/q4_input.txt ./bin/charfreq | less
- $ # look for strings w/high-frequency bytes
+
+Look for strings w/high-frequency bytes and you'll find the following
+w/five hits of ASCII-encoded 21. There's another input in which ']' gets five
+hits, but it doesn't seem to decrypt to anything.
+
$ INPUT=7b5a4215415d544115415d5015455447414c155c46155f4058455c5b523f
$ HIGH_FREQ_BYTE=21
$ echo $INPUT | ./bin/single_byte_xor $HIGH_FREQ_BYTE
@@ -56,6 +83,14 @@ This is illustrated for 1.1.
xored with: 21 ()
decrypted: nOWTHATTHEPARTYISJUMPING*
+Similar here, using 21 + 32:
+
+ $ echo $INPUT | ./bin/single_byte_xor 53
+ original: 7b5a4215415d544115415d5015455447414c155c46155f4058455c5b523f
+
+ xored with: 53 (5)
+ decrypted: Now that the party is jumping
+
#### 1.5
$ echo -n $(< data/s1/q5_input.txt) | ./bin/repeating_key_xor ICE | fold -w 74
@@ -66,21 +101,33 @@ This is illustrated for 1.1.
0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a2622632427276527
2a282b2f20690a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f
+Can check this by grabbing the result under 'INPUT' and xor-ing it again:
+
+ $ xxd -r -p <<< $INPUT | ./bin/repeating_key_xor ICE | xxd -r -p | less
#### 1.6
$ INPUTB64=$(< data/s1/q6_input.txt)
$ INPUTHEX=$(echo $INPUTB64 | ./bin/b642hex)
$ echo $INPUTB64 | ./bin/score_keysizes 4 10
- $ # top keysizes for average of 4+ groups are roughly 5, 29, 3
+
+Top keysizes for average of 4+ groups are roughly 5, 29, 3.
+
+Five doesn't go far:
+
$ KEYSIZE=5
$ echo $INPUTHEX | ./bin/rotate $KEYSIZE | parallel -k ./bin/charfreq | less
+
+Twenty-nine does it:
+
$ KEYSIZE=29
$ echo $INPUTHEX | ./bin/rotate $KEYSIZE | parallel -k ./bin/charfreq | less
$ xxd -r -p <<< "$INPUTHEX" | \
./bin/repeating_key_xor "tERMINATOR x bRING THE NOISE" | \
xxd -r -p | less
- $ # shift by 32 for readability
+
+Shift by 32 for readability:
+
$ xxd -r -p <<< "$INPUTHEX" | \
./bin/repeating_key_xor "Terminator X: Bring the noise" | \
xxd -r -p | less
