Dump payload from a SMART Health Card https://smarthealth.cards/

shc.py

# This code is dedicated to the public domain under
# Creative Commons CC0 1.0 Universal <https://creativecommons.org/publicdomain/zero/1.0/>

import base64
import json
import sys
import zlib

shc = input()

SHC_PREFIX = "shc:/"

def get_numbers(digits):
    for i in range(0, len(digits), 2):
        yield int(digits[i:i+2])

if not shc.startswith(SHC_PREFIX):
    print("Invalid: Does not start with required prefix")
    sys.exit(1)

shc_digits = shc[len(SHC_PREFIX):]

if "/" in shc_digits:
    print("Unsupported: Multi-segment code")
    sys.exit(1)

if len(shc_digits) % 2 != 0:
    print("Invalid: Odd number of digits")
    sys.exit(1)

jwt_text = "".join(chr(x + 45) for x in get_numbers(shc_digits))
jwt_components = jwt_text.split(".")

payload_component = jwt_components[1]
padded_base64_payload = payload_component + ("=" * (4 - len(payload_component) % 4))
compressed_payload = base64.urlsafe_b64decode(padded_base64_payload)
payload = zlib.decompress(compressed_payload, wbits=-15)

print(json.dumps(json.loads(payload.decode("UTF-8")), indent="\t"))