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12

I've been suggested to digitally sign it, thus, I have my private key, and I ship my application with a public key, and the application then uses the public key to check the QR code As long as you can live with the requirements for RSA (signature size, computation), that sounds like an excellent idea. Am I encrypting the whole message using the private ...


9

Is there any worthwhile way to authenticate the message using only these functions and simple checksums? As usual, of course there is: AES-CCM! AES-CCM basically is CTR mode with a tagged-on CBC-MAC and length prepending. You can implement CTR trivially using your ECB primitive and CBC-MAC shouldn't be too hard to implement given a CBC primitive and ...


4

To your questions: You are not encrypting anything. Signing something with RSA is basically the same algorithm as decryption but some things are different (see below). No. You can generate one keypair and then use it for encryption, decryption, signing and verification. To help you with your task: Getting this right is not easy. If you have no ...


1

It's true that anyone who learns the master key has enormous leverage. Key management best practices are worth investigating. I highly recommend that you consider using a key management service (KMS) that is backed by a hardware security module (HSM). There are affordable offerings in cloud-based services, such as Amazon's Key Management Service, that ...


1

You could use the turtle block cipher with CMAC, maybe. The turtle block cipher claims a cipher design that is based on "an NP-Complete Subproblem". Block ciphers can be used to produce authentication tags via algorithms such as CMAC. I'm not sure if this combination necessarily qualifies the authentication as being based on an NP-Complete subproblem ...


1

The commit that added this double HMAC only says it improves "valid MAC detection", but it simultaneously adds the constant-time comparison, so likely the reason is indeed defense against timing attacks: Improve valid MAC detection Implement constant time string comparison as well as double HMAC verification for encryption MACs. Double HMAC is a ...



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