Questions tagged [message-recovery]

Message recovery is a feature of some digital signature schemes, whereas some or all of the message signed is embedded in the signature, recovered as part of signature verification, and thus needs not be transmitted.

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In ISO/IEC 9796-2 (signature with message recovery), why are some message representatives bigger than the modulus?

I have implemented signature scheme 2 from ISO/IEC 9796-2 in C using OpenSSL for the underlying crypto operations. To generate the message representative (F in the ...
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1answer
215 views

Why ISO/IEC 9796 (signature with message recovery) instead of just encrypt the short message with private key?

I've had a look at “Practical Cryptanalysis of ISO/IEC 9796-2 and EMV Signatures” and read the very good answer https://crypto.stackexchange.com/a/17846/59673 and I understand that signature and ...
2
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1answer
145 views

Build a cipher that is secure against message recovery attack but not semantically secure

I know the definitions of both of the securities (against message recovery and semantic), but I don't know how to actually build a cipher that meets these conditions, I mean, I don't know how to ...
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0answers
606 views

RC4: Find the complete plain text of a ciphertext when we know part of the plaintext

I need to decrypt an encrypted file with RC4 to answer to a Internet challenge. The file in question is a dump of a Teensy ROM and it is completely encrypted. Luckily, it looks like it's a standard ...
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1answer
281 views

Cryptanalys of “bad” RC4 implementation

I need help of cryptanalyzing a "bad" RC4 implementation to recover an encrypted text of 13742 bytes. I don't know the key and this implementation does not utilize the drop-n routine. But, I know ...
5
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1answer
120 views

Minimizing size of signed message with discrete-log scheme

How can we sign a small message with a discrete-log scheme so as to minimize the size of the whole signed message? Detailed objectives, notation: It is of paramount importance to minimize the total ...
17
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1answer
676 views

Message-Recovery variant of Ed25519 signature?

What would be a Message-Recovery variant of the Ed25519 signature scheme? Ed25519-MR should be simple to use, fast, with a strong security argument, and striving to stay out of the patent minefield, ...
2
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1answer
1k views

Forgery attack against Textbook RSA with simple redundancy

I know how to forge vanilla Textbook RSA message signatures (easy). I've learnt that by adding a good redundancy to the message, it cannot be forged anymore. How can one add redundancy so that the ...
8
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1answer
4k views

Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)

I'd like to get an overview of how the signatures with message recovery work, especially in case EMV and other smart card systems. Is there a nice overview available without being required to read the ...
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2answers
784 views

Any real world implementation using message recovery?

During my master thesis I came across RSA-PSS-R which is in my opinion a quite elegant way of saving bandwidth and space using digital signature. But I didn't find any information about any real world ...