CodesInChaos
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 18h comment Examples of modern, widely used ciphers that suddenly fell? Was RC4 already a major cipher when it fell to cryptoanalysis in 1995, merely a year after being published? 20h answered Strength of $H(k\|H(m))$ as a MAC algorithm 1d revised Is Schannel supposed to use SHA1 for (EC)DHE params? edited tags; edited tags 1d revised Can I get successful signature verification with just altering message and signature? edited tags 1d revised RSA signatures without padding edited tags 1d comment What are the advatages or disadvatages of using seperate chaining over linear or quadratic probing? It sounds to me like this question is about data-structures (hash tables). Could you explain how this relates to security or cryptography? 1d comment Is there a cryptographic function or system in which it becomes HARDER to break as time passes? @E.Rose Post quantum crypto, like McEliece, NTRU, hash signatures. There is some work on moving these from theoretical schemes to something used in practice. Apr 29 comment What is the private key in RSA? Personally I wouldn't call $d$ the private key, because it can't decrypt on its own. I'd just refer to it as the private exponent. Apr 28 revised Is this cascading encryption, and is my security weakened as a result? deleted 10 characters in body Apr 28 reviewed Approve Is this cascading encryption, and is my security weakened as a result? Apr 26 awarded Nice Answer Apr 25 comment What implementation properties of a hash function prevent safe truncation? I feel comfortable truncating SHA2 as long as the truncated size is sufficient for my desired security level. NIST does so as well (consider SHA-512/256 as an example) Apr 24 comment RSA when n= 2360221 and encryption = 5 find decryption key d, when M =1234 1) Factor n 2) Follow the wikipedia article on RSA to compute d. | hint: $2360221 = 1117 \cdot 2113$ Apr 23 comment What is the fastest block cipher in the (Intel) world? ChaCha isn't really a fair comparison, since it's only an unkeyed permutation, not a block cipher. Adding a key schedule costs some performance. I think @orlp got down to 2-3 cpb using SSE2 to implement a Blake2s derivative in OCB mode (10 rounds, corresponding to 20 ChaCha rounds). Apr 22 comment What is the fastest block cipher in the (Intel) world? Depends on the CPU, using AES-NI instructions AES is very fast (especially AES-128). Apr 20 comment Is the 'nonce' in bitcoin really a nonce? Even with a stream cipher, the nonce doesn't need to be unique. It's the (key, nonce) tuple that's unique. Apr 20 reviewed Approve The role of the dealer in visual cryptography Apr 19 comment Exploiting XOR one-time-pads with dictionary length that isn't a power of 2 Computer based implementations almost always operate on sequences of bits/bytes which obviously are powers-of-two. Classical implementations often use modular addition. Apr 19 comment Exploiting XOR one-time-pads with dictionary length that isn't a power of 2 How would you even implement xor over an alphabet that isn't a power-of-two? Apr 19 reviewed Approve Are the definitions of IND-CCA secure and of IND-CCA secure under standard model identical?