I wasnt able to cracked it in 5minutes.
Maybe I would be able to in a few hours, if needed.
Anyway, the answer to your question is: it looks easy to crack.
As Pmalek said, reinvent security ia not a good idea. Why don't you look for a real encryption method? Such as using a passphrase?
Notedown the seed and add the 13rd word, the passphrase. It can be a word, a letter , a music, whatever you want. This will add security to your method. your coins will be safer using this method.
That wasn't the question. The question was if it IS easy to crack, not what it looks like.
Of course, reinventing the wheel is not a good idea. Maybe we should get in contact with Jim Dunlop and let him know that. Why not using a passphrase? I'm using one! Really?
Obviously, by looking at the string you posted in the OP, no one can come to the conclusion that those are Spanish words translated from English and written down backwards. Not only that, but they were also inserted into that Argentinian book you mentioned. So if you only want a straight answer to the question if that is easily recoverable. No, it isn't. I am going to refrain from commenting on anything else then.
Thank you! That is as close to a good answer as I can hope for, considering. I'll take it.
Yes, it's difficult question since i doubt anyone here have qualification as security auditor.
There are a number of members here who clearly know a lot about security. You don't need to be a security auditor to know how to crack a string.