[Android Software/Hacking General [Developers Only]] EskimoAlva:
i was just trying to get a grasp on how to flash bootloaders on android devices. I have got a grasp with how to do it on old WinMo HTC devices, but there seems to be a lot more information regarding the various Android handsets. So here is the rundown of what I have found so far:

General Android: it appears that almost all android phones have the ability to flash from an SD card (by putting an update.zip on it). Can this reflash the bootloader? i don't see a reason why not (the bootloader should be in memory when the updater is running, so the flash should be writable) but having said that, i know on the old HTC devices that I have used, it wasn't possible (you had to load a softSPL or a diagnostic SPL to then run the flashing). Also, would anyone by any chance have a good understanding of what is in the update.zip? i see it referenced a lot, but as far as i can tell, it looks like it is just packages and directories and stuff to copy. Most of the posts I have seen regarding flashing also try replacing the recovery image, and then booting into recovery and telling it to recover. Does this work for bootloaders or just ROMs?

HTC: this appears to be the same as the old WinMo 6 devices I have used. You can use the RUU utility, supply it with an nbh file, and there are no problems. Outside of the Incredible S it would also appear that they don't have any kind of signing or anything to worry about. As such, you can see the SPL in cleartext and is in cleartext on the phone (I am guessing anyways). One question I do have is I have the ancient NBHGen used for the Kaiser (also worked for Hermes, Trinity, etc.), will that work with say the HTC Hero (or insert modern phone here)?

Samsung: Samsungs SBL as far as I can tell is equivalent to the HTC SPL (much the same as the HTC IPL = Samsung PBL). I have actually seen an apk that supposedly updated the SBL for Samsung. Like HTC, it also appears that they leave everything in clear text. If i am not mistaken, Odin is the tool of choice for reflashing on Samsung devices (any good tutorials out there for it and its file formats? i haven't actually looked too hard at that yet)

Motorola: I dont wish to stir up any anger (especially since most of what I read is on the Droid X), but Motorola is the one that is the hardest to find real info on. Motorola, on their more popular phones, appears to have made a habit of adding aggressive anti-tampering to their premier phones (at least after the original droid). I don't believe that their SPL equivalents have been cracked, but I also can't find a straight answer about whether their bootloaders are signed or encrypted (or both). They are two different things, but have been largely used interchangeably on most forums. They also have eFuse protection. I have looked at a few of the SBF files in a hex editor, and they don't appear to be ARM assembly. That said, I wouldn't believe that it is encrypted as there is cleartext within it. This leaves a couple of options. either the data moved is encrypted and it copies over encrypted data that gets decrypted at boot time (that seems like a massive waste of CPU cycles, but i wouldn't put it past them to do something like that). Or it could mean it gets decrypted by whatever loads it onto the phone. And lastly, it could just be x86 assembly (which i wouldn't recognize by looking at it). The last one seems to be the best fitting, but it doesn't answer whether or not it is encrypted on the phone. Since I haven't found an SBF file that contains just a bootloader, i haven't really had the chance to examine it. I also have not sen a way to flash a new SPL to a device (even a more open one like the original droid, which i believe is still locked, just not signed/encrypted).

file formats: this is also kind of confusing. I mentioned the update.zip above, but i have also seen people referencing ,bin and .img and all kinds of other files. If i am not mistaken, a bin and img file are the same with a different extension. Straight up binary, though i believe that the img files are supposed to be partition images. Is that accurate? and are SBF files executable? i swear i saw somewhere that people were running them, though it could just be my imagination...

I know there is a lot there a lot of information there, but I just wanted to check and make sure it is accurate, so I don't sound like a noob to my boss when I present it.

Many thanks!