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


Oct
20
revised ZIP 2.0 encryption bruteforce attack
More references; polish
Oct
20
comment Serpent 256bit key wrong round keys
The Serpent Proposal, top of page 7 defines $w_{−8}\dots w_{−1}$. That allows applying $w_i=(w_{i-8}\oplus w_{i-5}\oplus w_{i-3}\oplus w_{i-1}\oplus\phi\oplus i)\lll 11$ including for $i=0\dots 7$. $\;$ Please fix the question accordingly, and tell us if any issue remains. $\;$ Also: use $\TeX$, that's easy! Your formula is written $w_i=(w_{i-8}\oplus w_{i-5}\oplus w_{i-3}\oplus w_{i-1}\oplus\phi\oplus i)\lll 11$.
Oct
20
revised ZIP 2.0 encryption bruteforce attack
improve link to late PKZIP 2
Oct
20
revised ZIP 2.0 encryption bruteforce attack
Update with link to info relevant to early PKZIP RNG
Oct
20
answered ZIP 2.0 encryption bruteforce attack
Oct
18
comment What is the history of recommended RSA key sizes?
[reposted with correction] As of the embedded world: one of two RSA keys with 321-bit public modulus has been used by French banks as global keys for static issuing certificates of credit/debit Smart Cards, well after the end of the 20th century (but are phased out now). See references in the third bullet point of this answer. The lowest routinely used nowadays is more like 1024-bit (e.g. European tachograph cards).
Oct
17
comment How secure would HMAC-SHA3 be?
@Richie Frame: the Keccak submission (and NIST slides I just added) seem to use the bitrate $r$ as block size, without the at least as large as $c$ condition that you suggest. I am without informed opinion.
Oct
17
revised How secure would HMAC-SHA3 be?
Add reference to NIST slides
Oct
17
comment What is the history of recommended RSA key sizes?
One data point: the original (1974) RSA paper said: "We recommend that $n$ be about 200 digits long." That was about 664 bits.
Oct
17
revised Database row level encryption scheme
Expand per comment
Oct
17
comment Compare two approaches for cracking RSA key
@Samuel Judson: for the first part, you have the right order of magnitude, but a) the number of 1536-bit primes is about half of what you estimate; b) what's the lowest possible value for the highest of the two primes? That allows another significant reduction. $\;$ For the second part, you have given an order of magnitude of the effort involved in generating the key. The question asks to turn this into a factorization method for the key at hand, without assuming prior knowledge of the password. $\;$ Side hint: the part of the answer reading "We'll have to do this twice" is wrong.
Oct
16
revised Are LFSRs enough for this?
Better explain the origin of the conjectured security bound.
Oct
16
revised Are LFSRs enough for this?
My conjecture is only tentative!
Oct
16
comment Are LFSRs enough for this?
I now have a tentative conjecture about a safe setup, with the colluding players never consecutive, and separated by $h$ honest ones.
Oct
16
revised Are LFSRs enough for this?
A try at a condition that would insure an adversary can't succeed
Oct
15
comment Is there any existing cipher capable of scaling from a 1 bit key up to a one-time-pad?
The criteria that given ciphertext and $b$-bit key, $2^b$ distinct plaintexts are possible $\;$ a) Can not be reached at all for key/plaintext ratio above 1, even though that is considered in the question. $\;$ b) Is NOT enough to give a useful level of confidentiality for other ratio (proof: consider encryption by XOR with key padded with zeroes up to plaintext length); that criteria can however be a compatible addition to more standard security criteria, at least if we allow about $2^b$ possible distinct plaintexts.
Oct
15
comment Is there any existing cipher capable of scaling from a 1 bit key up to a one-time-pad?
Note that the one-time-pad is not a cipher, by the modern definition, which requires key size to be fixed for arbitrary or much larger plaintext size. $\;$ I know no existing algorithm answering the question. It seems feasible to build one from existing primitives, but exactly what would be the desired security criteria?
Oct
15
revised Database row level encryption scheme
Security CAN be lower if a human is allowed to choose the pass-phrase; add AES-GCM
Oct
15
revised Database row level encryption scheme
Expand
Oct
15
answered Database row level encryption scheme