Ulrik Sverdrup wrote: > The blowfish encryption mode is vulnerable (not to revelation of the > plaintext), but the encryption is not checked for integrity or > authenticity. This means that someone might corrupt the encrypted file > (hexedit or similar), and vim will decrypt it without notice of error or > warning. > > This attack allows someone to modfiy encrypted files so that the owner > doesn't notice. With sufficient tries or skill it might be possible to > change a file's values in a predictable way at a certain offset. > > The solution is an authenticated encryption mode. The common way to do > it is 'Encrypt-then-MAC' where a message authentication code is formed > from the ciphertext and the key. This code when matching will prove that > the document is unchanged and was produced by someone with access to the > key. This code will detect the previous attack case, and additionally it > allows vim to detect that the wrong password was entered. Security > practise says that Vim must fail with an error if the MAC does not match.
I think that a verification key will actually make it easier to crack the password. Currently, when an attacker tries all kinds of passwords, he also needs a way to verify the decrypted text is actually readable. That is not so easy to do. With a verification key the verify part becomes really easy and fast. It is extremely difficult to change the file in a way that after decryption it is readable text. Probably just as difficult as cracking the password. When knowing that a file is only plain text, checking for invalid Unicode characters is probably sufficient to notice that the decryption failed. -- Communication is one of the most compli..., eh, well, it's hard. You know what I mean. Not? /// Bram Moolenaar -- [email protected] -- http://www.Moolenaar.net \\\ /// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\ \\\ an exciting new programming language -- http://www.Zimbu.org /// \\\ help me help AIDS victims -- http://ICCF-Holland.org /// -- -- You received this message from the "vim_dev" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups "vim_dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
