openx price decryption

pricedecrypt.py

# The incoming encrypted price is unpadded websafe base64 encoded of length 38
# This is obtained from base64 encoding the encrypted price, and *then*
# websafe base64 encoding the already encoded encrypted price.

encrypted_price_base64_wsbase64 = 'SjpvRwAB4kB7jEpgW5IA8p73ew9ic6VZpFsPnA'

# We first add padding

encrypted_price_base64_wsbase64_padded = 'SjpvRwAB4kB7jEpgW5IA8p73ew9ic6VZpFsPnA=='

# We decode the web safe base64 encoding

encrypted_price_base64_padded = base64.b64decode(encrypted_price_base64_wsbase64_padded, "-_")

# encrypted_price_base64_padded = 'J:oG\x00\x01\xe2@{\x8cJ`[\x92\x00\xf2\x9e\xf7{\x0fbs\xa5Y\xa4[\x0f\x9c'
# This is python formatted hex string of size 28. \x is an escape meaning the next two characters
# are hex digits and count as 1 character

# The result is a concatenation of a 16-byte initialization vector, 8 bytes of ciphertext, 
# and a 4-byte integrity signature

init_vector = 'J:oG\x00\x01\xe2@{\x8cJ`[\x92\x00\xf2'
cipher = '\x9e\xf7{\x0fbs\xa5Y'
integrity = '\xa4[\x0f\x9c'