In which zone of ​​a flash memory could a write that will not get erase by formatting

[Rabbit]

I don't know what it is that you're trying to accomplish. What you asked for at the beginning seems to have changed at this point. Originally, you asked if there's a way to write to flash memory so that it can't be erased. The answer to that is a resounding no, not without writing custom firmware. However, now it seems that you just want to make a file unreadable, not undeletable. In this case, there's no need to create a custom disk format, just encrypt the file or file system. The end result will be that the file will not be readable.

[Gilberto Gil]

Rabbit, maybe I have not been clear enough..so..
I've two thing to accomplish. the first was really that i posted here....In which zone of a flash memory could a write that will not get erase by formatting......but, as you said it can't be done without writing custom firmware. I've already understood that..
The second that I need to do is to protect the information inside flash memories, it's right that I could encrypt the file but the file will be still seen by common users(and that is not what i want) otherwise I could use some encryption software(TrueCr ypt for example) but it is not my own code, and i really dont't know if it has some back door or something like that..the other that you are telling me is to encrypt the file system. what do you mean with that, that i could encrypt for example FAT32 system wich is inside the flash that windows could not understand that and then couldn't see the information inside the flash memorie? if so it is really what i want to do.. for that reason I've been thinking in my own format because windows or another couldn't read that and common users couldn't see the information inside the flash without a program built by me that implement all the operation such as copy, paste, delete etc etc ... don't forget that i don't care if the memory is formated with another file system after mine..
I'm glad to see that there are people who help... thanks a lot

[Curtis Rutland]

otherwise I could use some encryption software(TrueCr ypt for example) but it is not my own code, and i really dont't know if it has some back door or something like that

It's far, far, far more likely that your own custom code will have "backdoors" (or more likely bugs) than TrueCrypt will. TrueCrypt is a well-know, well-trusted name in whole and partial disk encryption that's been under active development for seven years now. It's crazy to think you'll be able to put together something similar by yourself in a short time.

Don't re-invent the wheel. If this isn't just some programming exercise, and it's something you actually need, and need to work well, use proven software.

We've understood what you've been saying, we're just telling you things you don't want to hear.

[Rabbit]

You do realize that if the user formats the drive after you've done whatever you want to do to the disk means you lose all the information on there right?

I would just use TrueCrypt to encrypt the entire disk, it does what you're attempting to do by yourself but at a security level much higher than you're going to be able to achieve. TrueCrypt is open source so if you're worried about backdoors, just go over the code yourself. And whatever encryption scheme you're going to come up with is going to be many many times less secure than using AES, Serpent, or Twofish. All of which come with TrueCrypt.

[Gilberto Gil]

Thanks a lot. really.....you have convinced me.. i'll check TrueCrypt out...really I'm very grateful...