jm + sha1 + hashing   5

BLAKE2: simpler, smaller, fast as MD5
'We present the cryptographic hash function BLAKE2, an improved version
of the SHA-3 finalist BLAKE optimized for speed in software. Target applications include
cloud storage, intrusion detection, or version control systems. BLAKE2 comes
in two main flavors: BLAKE2b is optimized for 64-bit platforms, and BLAKE2s for
smaller architectures. On 64-bit platforms, BLAKE2 is often faster than MD5, yet provides
security similar to that of SHA-3. We specify parallel versions BLAKE2bp and
BLAKE2sp that are up to 4 and 8 times faster, by taking advantage of SIMD and/or
multiple cores. BLAKE2 has more benefits than just speed: BLAKE2 uses up to 32%
less RAM than BLAKE, and comes with a comprehensive tree-hashing mode as well
as an efficient MAC mode.'
crypto  hash  blake2  hashing  blake  algorithms  sha1  sha3  simd  performance  mac 
april 2016 by jm
NYC generates hash-anonymised data dump, which gets reversed
There are about 1000*26**3 = 21952000 or 22M possible medallion numbers. So, by calculating the md5 hashes of all these numbers (only 24M!), one can completely deanonymise the entire data. Modern computers are fast: so fast that computing the 24M hashes took less than 2 minutes.

(via Bruce Schneier)

The better fix is a HMAC (see ), or just to assign opaque IDs instead of hashing.
hashing  sha1  md5  bruce-schneier  anonymization  deanonymization  security  new-york  nyc  taxis  data  big-data  hmac  keyed-hashing  salting 
june 2014 by jm
fail0verflow ::
Excellent demo of how use of a block cipher with a known secret key makes an insecure MAC. "In short, CBC-MAC is a Message Authentication Code, not a strong hash function. While MACs can be built out of hash functions (e.g. HMAC), and hash functions can be built out of block ciphers like AES, not all MACs are also hash functions. CBC-MAC in particular is completely unsuitable for use as a hash function, because it only allows two parties with knowledge of a particular secret key to securely transmit messages between each other. Anyone with knowledge of that key can forge the messages in a way that keeps the MAC (“hash value”) the same. All you have to do is run the forged message through CBC-MAC as usual, then use the AES decryption operation on the original hash value to find the last intermediate state. XORing this state with the CBC-MAC for the forged message yields a new block of data which, when appended to the forged message, will cause it to have the original hash value. Because the input is taken backwards, you can either modify the first block of the file, or just run the hash function backwards until you reach the block that you want to modify. You can make a forged file pass the hash check as long as you can modify an arbitrary aligned 16-byte block in it."
crypto  hashing  security  cbc  mac  sha1  aes 
january 2013 by jm
Stop using unsafe keyed hashes, use HMAC
why HMAC is more secure than secret-suffix and secret-prefix keyed hashing. good to know
hmac  security  crypto  hashing  md5  hashes  sha256  sha1  from delicious
october 2009 by jm

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