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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 3 months
seen 3 hours ago

Jun
19
comment Are there standards for transport layer security using only symmetric keys?
If you have hardware AES, does that mean that other cryptographic functions, such as SHA1 are much slower than AES? In that case I'd consider an AES based MAC, such as CBC-MAC.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
Most SSL libraries are rather big. He'll need a specialized embedded SSL library.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
"keys actually change over time" How does that work? I don't remember anything of that kind being in non ephermal suites.
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
Can you give numbers for very little flash/RAM?
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
Do your embedded devices have access to a good entropy source? Can you generate reliable nonces?
Jun
19
comment Are there standards for transport layer security using only symmetric keys?
You'll need to be careful about using IVs and MACs correctly. Plain AES-CBC is vulnerable to active attacks.
Jun
19
comment Can you distinguish encryption methods from the output?
Cross post: stackoverflow.com/questions/11072921/…
Jun
18
comment Why are there $ signs in my passwd file?
The standard attack vector is guessing the password. Since GPUs are fast, you can use many password candidates.
Jun
18
revised Why are there $ signs in my passwd file?
added 24 characters in body
Jun
18
answered Why are there $ signs in my passwd file?
Jun
18
comment Is ECB mode secure if plaintexts guaranteed to be unique?
I just want to emphasize that people often underestimate the severity of attacks against unauthenticated modes. A 16 bit checksum is nice to protect against random errors, but not enough to protect against malicious modifications.
Jun
17
comment Is this password migration strategy secure?
Looks perfectly fine to me.
Jun
15
comment Why is ciphertext from low entropy plaintext not compressible?
Compressing a ciphertext implies breaking the encryption. Since the best known algorithms for breaking AES are very expensive (about 2^128 operations), the best known algorithms for compressing the ciphertext are at least as expensive.
Jun
11
comment Is this streamable combination of encryption and MAC secure?
With CTR mode, you don't need to include $IV_i$, but you still need to include the block number. Else the reordering is still possible, and will result in corrupted plaintext. At least if you use a encrypt then MAC mode.
Jun
11
comment Encryption vs. decryption of same plaintext
That depends on the mode. Most secure modes use an IV to prevent both of them.
Jun
11
comment How did LinkedIn “salt” all their passwords?
I'd go with the second unless your website regularly deletes inactive users. For a typical website I'd expect most users to be inactive.
Jun
11
comment Is this streamable combination of encryption and MAC secure?
If you don't include $ IV_i $, random read access becomes much harder, since you still need to verify the IV somehow. Else the attacker can modify the IV, allowing him to modify your first plaintext block without you noticing. This assumes that the last block of the previous part serves as IV for the current part. If you use a different method for deriving the IV, this might not be necessary.
Jun
10
comment Okay to use OpenSSL to encrypt then sign a message?
Everybody sees who signed the message.
Jun
10
revised What's the reason for applying the hash twice when hashing with salt?
added 323 characters in body
Jun
9
comment What's the reason for applying the hash twice when hashing with salt?
right. Thanks..