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1500 questions
41
votes
2 answers
Why do we use encrypt-decrypt-encrypt (EDE) in 3DES, rather than encrypting three times?
I'm wondering why we use encrypt-decrypt-encrypt (EDE) sequence in 3DES (also known as DES-EDE, TDES or TDEA) with three keys instead of three times encryption (EEE) with three different keys?
alaamub
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41
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1 answer
What is Attribute Based Encryption?
Can someone explain what attribute based encryption is?
I was searching for a book or something that can help me in this regard but so far I have found none. Google also returns practically nothing aside from the papers.
Mark
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41
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3 answers
How is the MD2 hash function S-table constructed from Pi?
For fun, I'm learning more about cryptography and hashing. I'm implementing the MD2 hash function following RFC 1319 (https://www.rfc-editor.org/rfc/rfc1319). I'll preface by saying I know there are libraries, I know this is an old hash, and I do…
Keith
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40
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1 answer
RIPEMD versus SHA-x, what are the main pros and cons?
RIPEMD is a family of cryptographic hash functions, meaning it competes for roughly the same uses as MD5, SHA-1 & SHA-256 do. The Wikipedia page for RIPEMD seems to have some nice things to say about it:
"designed in the open academic…
user950
40
votes
9 answers
What's the truth about this "absolutely unbreakable" cipher?
A story appeared on Forbes today claiming that we now have an absolutely unbreakable cipher. It cites a paper published in Nature Communications. However, I'm skeptical:
But what if there were a method of enabling data to be sent using an…
Joseph Sible-Reinstate Monica
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40
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1 answer
Why do the elliptic curves recommended by NIST use 521 bits rather than 512?
Wikipedia says in reference to the elliptic curves officially recommended by NIST in FIPS 186-3:
Five prime fields for certain primes p of sizes 192, 224, 256, 384, and 521 bits. For each of the prime fields, one elliptic curve is recommended.
The…
Zack Elan
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40
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1 answer
ECDSA, EdDSA and ed25519 relationship / compatibility
I'm trying to understand the relationship between those three signature schemes (ECDSA, EdDSA, and ed25519) and mainly to what degree they are mutually compatible in the sense of key-pair derivation, signing, and signature verification. But I was…
Rafael Korbas
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40
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1 answer
What is “Fast Prime”?
In this note, the manufacturer of a RSA key generation gizmo vulnerable to the new ROCA attack (see second section) explains that
it is common practice to employ acceleration algorithms in order to generate key pairs, especially if time resources…
fgrieu
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40
votes
2 answers
How does hashing twice protect against birthday attacks?
The bitcoin wiki says:
Bitcoin is using two hash iterations (denoted SHA256^2 ie "SHA256 function squared") and the reason for this relates to a partial attack on the smaller but related SHA1 hash. SHA1's resistance to birthday attacks has been…
4nt
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40
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3 answers
Why is CBC with predictable IV considered insecure against chosen-plaintext attack?
I just learned that using CBC encryption with an IV which is predictable is not secure.
From what I understand, using certain plain texts, and then guessing the IV that it uses, the attacker can verify if the IV he guessed was right. How does this…
asudhak
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40
votes
2 answers
How does order-preserving encryption work?
Order-preserving encryption (OPE) is, apparently, a method of encrypting data so that it's possible to make efficient inequality comparisons on the encrypted items without decrypting them.
I've been coming across this term in various places…
Ilmari Karonen
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39
votes
3 answers
Why was AES CBC removed in TLS 1.3?
I don't quite understand why AES CBC was removed in TLS1.3.
From what I know CBC is the most secure Mode of operation for the AES block cipher (if you can say it like that).
It only needs a TRND IV and has not been broken. If you pair it with a…
Richard R. Matthews
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39
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2 answers
HMAC vs ECDSA for JWT
I will be implementing JSON web tokens into my website and have a question about implementing them. I have a choice of using two algorithms, HMAC-SHA256 and ECDSA-SHA256. I have used HMAC-SHA256 in the past for jwt, but now I noticed ECDSA is being…
user2924127
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39
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4 answers
What is the recommended replacement for MD5?
Since MD5 is broken for purposes of security, what hash should I be using now for secure applications?
grieve
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39
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2 answers
Why is HMAC-SHA1 still considered secure?
This Q & A https://security.stackexchange.com/questions/33123/hotp-with-as-hmac-hashing-algoritme-a-hash-from-the-sha-2-family
says that the security of HMAC-SHA1 does not depend on resistance to collisions? Are they are saying specifically with…
user93353
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