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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Jan
26
answered How long will my encryption remain private?
Jan
26
comment Factorization or discrete logarithm is difficult for an attacker?
Are you using "signature" in its standard meaning, that is a value computed from data and a private key, allowing anyone knowing the corresponding public key to ascertain the integrity of the data without any secret information? Or some other meaning, perhaps that of Message Authentication Code?
Jan
25
comment How can I find the prime numbers used in RSA?
Alice did as explained [here])(people.csail.mit.edu/rivest/Rsapaper.pdf), but with a public key which would have been imprudently small even in 1978, thus you can solve the problem given the first number only, or be smarter and use all three.
Jan
25
revised How can I find the prime numbers used in RSA?
[Edit removed during grace period]
Jan
24
comment Shamir Secret Sharing Modular Reduction
MPC [thinking] Oh yes, Multi Party Computation.
Jan
24
revised How to protect against ephemeral key reuse in some signature schemes?
polish
Jan
24
answered How to protect against ephemeral key reuse in some signature schemes?
Jan
24
revised RSA with composite numbers
Fix problem with my proposed key generation
Jan
23
revised RSA with composite numbers
Expand correction
Jan
23
revised RSA with composite numbers
Clarify
Jan
23
comment ASCII to same-length ASCII encryption?
@Petr B: by a counting argument, it is not possible to reversibly encipher the $37^{15}$ possible strings in your input set into the $36^{15}$ strings in your desired output set.
Jan
23
revised Hash 22 byte secret into 512 bit hash: Full entropy?
Polish
Jan
22
comment ASCII to same-length ASCII encryption?
@Petr B; Both you butlast comment and question have the clear string using the set [A-Z0-9:] while the enciphered string uses the narrower set [A-Z0-9]. Is that a typo, or wanted? Without this, and assuming a computer can do the encoding/decoding, that's a straight case of format-preserving encryption
Jan
22
revised Hash 22 byte secret into 512 bit hash: Full entropy?
Expand and generalize, adressing Stephen Touset's comment. Reference to Shannon entropy.
Jan
22
revised A specific way for deniable encryption
Talk about (lack of) implementation
Jan
22
comment Regain 3DES ECB key, assuming I have both encrypted and decrypted text
That would amount to divination.
Jan
21
revised A specific way for deniable encryption
Consider the possibility that "The Hobbit" is embedded in the decoding program
Jan
21
comment A specific way for deniable encryption
@Shashank Sawant: the question is interesting as is; if the production of the ciphertext MJ could be without the "The Hobbit" as input (it can't, except if "The Hobbit" is hard-coded in the deciphering code), the system would allow deniability; if both "The Hobbit" and "Mocking Jay" are input in the production of the ciphertext MJ, the system is feasible, but then there's the problem stated in my last paragraph.
Jan
21
comment In what way is XXTEA really vulnerable?
AES-GCM, OCB, EAX are not full replacement for XXTEA: they lack the desirable property of XXTEA that, even with a stalled TRNG (a failure that is easy to induce for the adversary in a DRM context when enciphering on the user/adversary side), any change in any bit of plaintext leads to a change in any bit of ciphertext (with odds 1/2). Also, AES-GCM, OCB, EAX.. are vastly more complex to implement, thus vastly more likely to be implemented using existing code or system functions, which makes it considerably easier to recover the key in a DRM context.
Jan
21
comment Efficiently computing the neutral element in a ring isomorphic to Z/NZ?
You are of course right about the need for several tries, my mistake, oups!