Firstly, sorry that my script is not working for you. I tested it with a number of files and never got this error 
This part of the error message suggests that the checksum of the generated WIF format private key, doesn't match the original checksum from the private key stored in the file:
Is the .key file encrypted as well? Can you open it in a text editor like Notepad and read anything? If it is all encrypted, can you run the decrypt_multibit_classic_keys.py script on the .key file with that password? Does that generate any errors?
Unfortunately, I cannot replicate this error... so it is a little hard for me to test and figure it out...
I have made a quick modification here: https://pastebin.com/Z2zfbwiv
It should hopefully print out the "hex" version of the private key after the Pubkey: line... and before the error occurs. it'll look something like (NOTE: hex should be exactly 64 chars long):
Privkey: 41e09d37764805f234d2d17995d1c8f6338243f413a374c8d8a8b1e002b5b67e
Create an offline copy of the bitaddress.org website (links are at the bottom of the bitaddress.org page)... and then copy/paste that hex value into "Private Key" section of the "Wallet Details" page and click the "View Details" button. See if it gives you the matching addresses or an error message.
If you don't actually get that big long hex string (exactly 64 chars) from the script... then that is the reason for the error... as the private key is not being retrieved correctly... which is a bit of a problem
This part of the error message suggests that the checksum of the generated WIF format private key, doesn't match the original checksum from the private key stored in the file:
Quote
assert bin_dbl_sha256(data[:-4])[:4] == data[-4:]
AssertionError
AssertionError
Is the .key file encrypted as well? Can you open it in a text editor like Notepad and read anything? If it is all encrypted, can you run the decrypt_multibit_classic_keys.py script on the .key file with that password? Does that generate any errors?
Unfortunately, I cannot replicate this error... so it is a little hard for me to test and figure it out...
I have made a quick modification here: https://pastebin.com/Z2zfbwiv
It should hopefully print out the "hex" version of the private key after the Pubkey: line... and before the error occurs. it'll look something like (NOTE: hex should be exactly 64 chars long):
Privkey: 41e09d37764805f234d2d17995d1c8f6338243f413a374c8d8a8b1e002b5b67e
Create an offline copy of the bitaddress.org website (links are at the bottom of the bitaddress.org page)... and then copy/paste that hex value into "Private Key" section of the "Wallet Details" page and click the "View Details" button. See if it gives you the matching addresses or an error message.
If you don't actually get that big long hex string (exactly 64 chars) from the script... then that is the reason for the error... as the private key is not being retrieved correctly... which is a bit of a problem
Hi I have a similar problem. And really need help....
I have Multibit classic 0.5.19 with BTC in it back form 2013. When I try to send or export the keys the password bug mean the correct on does not work.
I have tried the multibit to Keepkey utlity and i get error message no balance.
I have the .wallet .key and .wallet.cipher files but they are encrypted.
I used this script on GitHUb. But it showed me error messages when I entered my password. I worked and showed me the keys for my other no passworded Multibit classic wallets.
https://github.com/Multibit-Legacy/read-multibit-wallet-file/tree/c4956f1c5a1ecb2df7a5612c8d9ea04388cdde0f
I got to this page but how do I run the python script on my Mac in Terminal?
https://pastebin.com/Z2zfbwiv
I hope this will work and will decrypt my .keys file. The BTC in there is worth a lot to me so any help will be appreciated.