trezor-firmware/src/apps/common/signverify.py

from ubinascii import hexlify
from trezor.crypto.hashlib import sha256
from trezor import ui
from trezor.ui.text import TEXT_MARGIN_LEFT
from trezor.utils import chunks, split_words, HashWriter
from apps.wallet.sign_tx.signing import write_varint


def message_digest(coin, message):
    h = HashWriter(sha256)
    write_varint(h, len(coin.signed_message_header))
    h.extend(coin.signed_message_header)
    write_varint(h, len(message))
    h.extend(message)
    return sha256(h.get_digest()).digest()


def split_message(message):
    try:
        m = bytes(message).decode()
        lines = split_words(m, ui.WIDTH - 2 * TEXT_MARGIN_LEFT, metric=lambda x: ui.display.text_width(x, ui.NORMAL))
    except UnicodeError:
        m = hexlify(message)
        lines = chunks(m, 16)
    return lines