Reputation
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20/20 answers
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Sep
10
comment 1024 RSA Hash Signature attack. Forge a valid signature
@fgrieu: if you could do $2^{85}$ work, you're better off just factoring the 1024 bit modulus...
Sep
10
answered 1024 RSA Hash Signature attack. Forge a valid signature
Sep
10
comment Fast 128-bit MAC with second preimage resistance?
Actually, otus specifically didn't ask for collision resistance; only second preimage resistance
Sep
10
revised Is there an encryption format that preserves length and only outputs alphanumerics?
edited tags
Sep
9
reviewed No Action Needed Decrypt using OpenSSL produces packing errors
Sep
9
reviewed No Action Needed How to deliver an encrypted message to multiple recipients without revealing keys
Sep
9
comment Is simple XOR with secret key using DHE secure?
@jakubinf: no, you still have to worry about the attacks that uer595228 pointed out.
Sep
9
answered Is simple XOR with secret key using DHE secure?
Sep
9
reviewed No Action Needed Is it safe to reuse a symmetric key when using asymmetric encryption?
Sep
9
awarded  Nice Answer
Sep
8
reviewed No Action Needed If my server utilises an RSA based certificate, why does firefox think I am using Diffie Hellman?
Sep
8
reviewed No Action Needed Triple-DES DUKPT CBC PIN variant vs Data variant
Sep
8
comment Efficiency of McEliece cryptography (ciphertext expansion)
@faith: because, whenever we use RSA to encrypt a message, we apply randomized padding (RSA without padding is insecure; at least, it makes it easy to test if a particular plaintext and ciphertext correspond), and this randomized padding expands the message.
Sep
8
comment Efficiency of McEliece cryptography (ciphertext expansion)
@faith: for a symmetric system, yes, that would be a cost which would be hard to justify. However, McEliece is an asymmetric system; for one, all asymmetric encryption systems have some ciphertext expansion, and secondly, in practice, it's used to transport the symmetric keys, hence we use it only once for an entire protocol exchange (and an expansion of less than 100 bytes is quite tolerable).
Sep
8
answered Efficiency of McEliece cryptography (ciphertext expansion)
Sep
4
comment Padding size with a CBC Block cipher in TLS
@chadianscot: no, you always have a padding length field. Otherwise, how would the decryptor know whether or not there is padding there?
Sep
3
reviewed No Action Needed Where is Signaturevalue in Certificate?
Sep
3
comment Do $v_1=\alpha\cdot r_1$ and $v_2=\alpha\cdot r_2$ leak information about $\alpha$
@user13676: I assume you meant "what if some of the $r_i$ values are smaller than $p/\alpha$. So what if that happens? How can the attacker get any information about whether that happens? As my answer stated, the values that the attacker sees is consistent with any nonzero $\alpha$. The attacker can guess that $r_i \cdot \alpha < p$, however without any way of validating that guess, that doesn't tell him anything.
Sep
3
answered Do $v_1=\alpha\cdot r_1$ and $v_2=\alpha\cdot r_2$ leak information about $\alpha$
Sep
3
answered TLS Cipher Suite definitions