encoding::obfuscation

file sample
xxd sample | head
python3 - <<'PY'
import base64
s='...'.encode()
for fn in (base64.b16decode, base64.b32decode, base64.b64decode, base64.urlsafe_b64decode):
    try: print(fn.__name__, fn(s))
    except Exception: pass
PY

echo 7069636f | xxd -r -p
echo cGljbw== | base64 -d
python3 -c "import urllib.parse;print(urllib.parse.unquote('%70%69%63%6f'))"

# to hex
echo -n pico | xxd -p

import base64, binascii, urllib.parse
data = b'cGljbw=='
base64.b64decode(data)
binascii.unhexlify(b'7069636f')
urllib.parse.unquote_to_bytes('%70%69%63%6f')

# keep bytes until final display

python3 -c "print(int('01110000',2))"
python3 -c "print((0xdeadbeef).to_bytes(4,'little'))"
python3 -c "print(int.from_bytes(bytes.fromhex('efbeadde'),'little'))"

file blob
binwalk -e blob
python3 - <<'PY'
import zlib,sys
raw=open('blob','rb').read()
for w in (zlib.MAX_WBITS, -zlib.MAX_WBITS, 15|32):
    try: print(w, zlib.decompress(raw, w)[:80])
    except Exception: pass
PY

python3 - <<'PY'
data = bytes.fromhex('3a2b2c')
for k in range(256):
    p = bytes(b ^ k for b in data)
    if b'flag' in p.lower() or all(9 <= c < 127 for c in p):
        print(k, p)
PY

# ciphertext = plaintext XOR key
# key = plaintext XOR ciphertext
python3 - <<'PY'
pt = b'picoCTF{'
ct = bytes.fromhex('0011223344556677')
key = bytes(a ^ b for a,b in zip(pt, ct))
print(key)
PY

tr 'A-Za-z' 'N-ZA-Mn-za-m'
python3 - <<'PY'
import string
s='uryyb'
a=string.ascii_lowercase
for k in range(26):
    t=''.join(a[(a.index(c)+k)%26] if c in a else c for c in s)
    print(k,t)
PY

python3 - <<'PY'
import base64,binascii
data=b'...'
changed=True
while changed:
    changed=False
    for fn in (base64.b64decode, base64.b32decode, binascii.unhexlify):
        try:
            new = fn(data)
            if new != data:
                print(fn.__name__, new[:80])
                data = new
                changed=True
                break
        except Exception:
            pass
print(data)
PY