Okay I just finished doing this for myself, so for anyone who wants to do this as well: Just create a text file named “contact_map.txt” that has the following format for each line:

signal_id,name,phone_number

The name isn’t really necessary, I just used it for my own book keeping while figuring out which signal ID corresponds to which of my contacts.

Then use the following python script to update all the numbers:

import numpy as np

contacts = np.loadtxt('contact_map.txt', delimiter=',', dtype='str')

with open('raw_backup.xml', 'r') as file:
    filedata = file.read()

for contact in contacts:
    filedata = filedata.replace('address="{}"'.format(contact[0]),
                                'address="{}"'.format(contact[2]))

with open('converted_backup.xml', 'w') as file:
    file.write(filedata)

I used another tool to get phone numbers. With https://github.com/pajowu/signal-backup-decode you can get the whole, decrypted Sqlite database. Messages and contacts are in different tables, but can be listed together with a join between the sms/mms and recipient table.

The internal database of signal (and as a result, the backup of that database) is under active development, while signal-back has not been modified in over a year. These compatibility drifts are inevitable.

Check out the fork at https://github.com/maximeborges/signal-back for a possible fix

Wow! Thanks a ton.