vb.net - AVRdude encrypt/decryption HEX file on the fly in VB -

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hey looking decrypt hex code file attiny chip , programming using avrdude command line interface. problem being, not want user able see hex file @ given time.

can vb.net cryptography crypt hex file before put onto server , decrypt after program downloads server , runs through program without seeing decrypted hex file?

obviously hex file can not stay encrypted while being programmed attiny chip how can go can create original hex file programmed within program without having worry writing temporary file hard drive , deleting afterwards? (because close program after temp file , able navigate , open , see code)

any great! :o)

david

as pointed out, if decrypt file on host there in unencrypted form, , can't that.

the industry has same problem time time, got ways cryptography: needed prevent else able compiled , runnable file "they" decompile or @ in assembly, needed prevent anyoneelse able run proper, home-brewn files on device.

as said, decrypting file on host (the users/clients host) out of question. push moment later. can, example, have bootloader decrypt firmware file reads serial line.

in case, deliver hardware (chip, bootloader , initial firmware version), , updates installed via serial line (instead of jtag/asp/isp). bootloader contain secret key decrypts firmware file. secret key can used verify firmware file coming you, , nobody else compiled something.

if need hand out bootloader (hex file) well, face problem extract or change secret key. in case, asymetric cryptography save you. keep private key you, , bootloader gets public key part. if able extract public key, not able create file recognized yours. alas, attiny far weak asymetric cryptography, , symetric cryptography bloat bootloader code.


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