Security notes / Unsorted

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Security related stuff.

Practical


Theory / unsorted

how to do a login system badly
how to do encryption badly
Disk and file encryption notes
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This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)


TPM

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

What?

Trusted Platform Module is part of the Trusted Computing design.


The TPM is basically the hardware part of that design.

Physically, TPM is often a hardware module that can be plugged into PC motherboards and laptops, and may be built into laptops (fairly common in business laptops).

One could also be part of a CPU (helps against some physical attacks), but there is some value to keeping it separate (e.g. if the CPU is upgradable).

(You could also implement the spec in code, but doing so means you lose the isolated environment, which defeats half the point)


The TPM is a few different things to different people/needs. It e.g. helps store some keys, creates derived keys without revealing the original, does certain crypto.


It being separate hardware

makes attack surface much smaller and some attacks much harder to do remotely,
makes it harder to steal keys,
means there are some cases where you can use a key it stored without every transporting it out.
...and that you can use some keys without having to keep them in RAM
Keys for some uses can be marked as "never move these out".
Some other uses require them to be migratable, though.
lets you tie certain keys to the specific TPM
which alleviates certain physical attacks.
For example, you can force an encrypted drive to only work on the computer you encrypted it on
you can prevent booting something that wasn't previously approved
as protection against malware that alters the boot
again, with footnotes.






"Can't detect TPM device"

Means the BIOS knows that you can plug in a TPM module, and is looking for it (being told to, or always does), and doesn't find one.

So tell it not to look for one (if you can), plug one in, or ignore this message. It's often under a header named something like 'Trusted Computing'

Some BIOSes will always look for it(verify), in which case you can just ignore the message.

More acronyms

What does TPM not protect?

TPM versus TPM2

Use and criticism, strengths and weaknesses

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

See also

Nonce

Challenge/response

ZKP

JSON Web Signature, Encryption, Tokens

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

JSON Web Signature (JWS)

Signing arbitrary data.

See also:


JSON Web Encryption (JWE)

Syntax for the exchange of encrypted data, and sending it in Base64 within JSON.

See also:


JSON Web Tokens (JWT)

JWT is aimed at sending verifiable claims, building on JWS or JWE

Signed using a shared secret, or a public/private key.

Typically used between identity provider and a service provider, in an SSO-like way.

See also:


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