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Why not modify the Update.zip?

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rhetorician
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Default Why not modify the Update.zip?

Forgive my ignorance, but couldn't one modify the update zip to include superuser and the corresponding library files? It seems others--who actually know what they're doing--do this process or something similar across many devices, with continued success. Am I missing something? Have I oversimplified?

Don't worry, I won't ask anyone to walk me through it If in fact it's a viable option (I can Google, read etc.). If is, though, I think it'd be a great learning experience.

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toastido
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Quote:
Originally Posted by rhetorician View Post
Forgive my ignorance, but couldn't one modify the update zip to include superuser and the corresponding library files? It seems others--who actually know what they're doing--do this process or something similar across many devices, with continued success. Am I missing something? Have I oversimplified?

Don't worry, I won't ask anyone to walk me through it If in fact it's a viable option (I can Google, read etc.). If is, though, I think it'd be a great learning experience.

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The problem is that the update zips are signed and will not flash without a valid signature outside of a custom recovery (which will trip Knox).

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rhetorician
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So modification of the stock image would not be viable via stock recovery unless, for example, one could, for a lack of better words, forge Samsung's signature?

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toastido
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Quote:
Originally Posted by rhetorician View Post
So modification of the stock image would not be viable via stock recovery unless, for example, one could, for a lack of better words, forge Samsung's signature?

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Correct. Since the signature is generated uniquely based in the hash of the file, a salt (usually the time) and a private key that only Samsung has, good luck "forging" the Sig :P We'd have better luck at finding a flaw in the signature verification than actually cracking the key.

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Devices:
2012 ASUS Nexus 7 - KitKat 4.4.4 Stock ROM - leanKernel(grouper) v4.0
T-Mobile Galaxy Note 3 - KitKat 4.4.2 Stock ROM(N900TUVUDNF4) - leanKernel(N900T) v3.6

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rhetorician
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Quote:
Originally Posted by toastido View Post
Correct. Since the signature is generated uniquely based in the hash of the file, a salt (usually the time) and a private key that only Samsung has, good luck "forging" the Sig :P We'd have better luck at finding a flaw in the signature verification than actually cracking the key.

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Understood. I have no intention of undertaking such a project, but it nevertheless helps me conceptualize the situation.

Thank you for clarifying!

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