Lösenordsknäckningsverktyget (woh, långt ord) John the Ripper är nu ute i version 1.7.9. Största ändringen är att OMP-patcharna (OpenMP) nu finns med som standard.

Changelog enligt följande (engelska)

Följ oss på Twitter: http://twitter.com/kryptera

Visste du att Amazon hyr ut datorkapacitet per timme? Ja, det vet nog de flesta. Men få vet att de även hyr ut kapacitet där en GPU (läs kraftfullt grafikkort) ingår. Från 2$ per timme så kan du få tillgång till en mycket kraftfull server för att utföra lösenordsknäckning med, här tänkte vi ge en liten guide till hur du kan komma igång och knäcka lösenord i molnet.

1. Skaffa ett Amazon Web Services-konto och gå in på EC2-konsollen för US-east.

2. Dra igång en ny server med ”Launch instance”-knappen och välj sedan Community AMIs fliken där du söker efter följande serverkopia: ami-aa30c7c3

3. Gå igenom alla steg och ställ in så du kan logga in på servern med ssh. Det kan vara lite bökigt om det är första gången du använder Amazon EC2.

När du väl kommit in så följer du denna guide:

Nu måste vi installer g++ kompilatorn:

Sedan måste vi kompilera biblioteken:

Dax att ladda hem och bygga + installera CUDA-Multiforcer:

Tyvärr så är dess Makefile lite felaktig så vi måste byta ut nedan rad

så den istället ser ut så här:

Sen är det bara att skriva make, om allt gick bra så bör du ha en fil här: ~/NVIDIA_GPU_Computing_SDK/C/bin/linux/release/CUDA-Multiforcer. Du kan sedan exekvera mjukvaran på följande sätt:

Grattis! Du har nu en helt egen lösenordsforcerare i molnet. Glöm inte att använda exempelvis -h FASTMD5 om det är MD5 du vill knäcka.

Grafikkortet som används i våra tester var NVIDIA Tesla M2050.

Gällande prestanda så får vi 487.3 miljoner MD5-försök per sekund.

Denna guide baseras på detta blogginlägg.

Följ oss på Twitter: http://twitter.com/kryptera

Nu har den populära knäckningsprogrammvaran John the Ripper släppts i en ny version, nämligen 1.7.7.

Ändringar är enligt följande (på engelska):

* Added Intel AVX and AMD XOP instruction sets support for bitslice DES (with C compiler intrinsics). New make targets: linux-x86-64-avx, linux-x86-64-xop, linux-x86-avx, and linux-x86-xop (these require recent versions of GCC and GNU binutils).
* A ”dummy” ”format” is now supported (plaintext passwords encoded in hexadecimal and prefixed with ”$dummy$”) – for faster testing and tuning of custom wordlists, rule sets, .chr files, and external modes on already known or artificial passwords, as well as for testing of future and modified versions of John itself.
* Apache ”$apr1$” MD5-based password hashes are now supported along with the FreeBSD-style MD5-based crypt(3) hashes that were supported previously. Hashes of both of these types may be loaded for cracking simultaneously.
* The ”–salts” option threshold is now applied before removal of previously cracked hashes for consistent behavior with interrupted and continued sessions.
* The ”Idle = Y” setting (which is the default) is now ignored for OpenMP-enabled hash types when the actual number of threads is greater than 1. (Unfortunately, it did not work right at least with GNU libgomp on Linux.)
* When a cracking session terminates or is interrupted, John will now warn the user if the cracked passwords printed to the terminal while cracking are potentially incomplete. It will advise the user to use the ”–show” option to see the complete set of cracked passwords with proper post-processing.
* When loading hashes specified on a line on their own (feature introduced in 1.7.6), the loader will now ignore leading and trailing whitespace.
* Unless a hash type is forced from the command line, the loader will now print warnings about additional hash types seen in the input files (beyond the hash type autodetected initially).
* For use primarily by the jumbo patch (and later by future enhancements to the official versions as well), the loader now includes logic to warn the user of ambiguous hash encodings (e.g. LM vs. NTLM vs. raw-MD5, all of which may be represented as 32 hexadecimal characters) and of excessive partial hash collisions, which it works around (these are typically caused by an incomplete implementation of a new hash type).
* The ”unique” and ”unshadow” programs have been made significantly faster.
* ”DateTime”, ”Repeats”, ”Subsets”, ”AtLeast1-Simple”, ”AtLeast1-Generic”, and ”Policy” external mode samples have been added to the default john.conf.
* The self-tests have been enhanced to detect more kinds of program bugs.
* A few minor bug fixes and enhancements were made.

John the Ripper 1.7.7 kan ladda hem här:

• download.openwall.net/pub/projects/john/1.7.7/

Följ oss på Twitter: http://twitter.com/kryptera

En ny attack mot MD5 har presenterats som gör det enklare att hitta kollisioner.

$ sed -r 's/(..)(..)(..)(..)/\4\3\2\1/g' m0.hex | xxd -r -p | md5sum
cee9a457e790cf20d4bdaa6d69f01e41  -
$ sed -r 's/(..)(..)(..)(..)/\4\3\2\1/g' m1.hex | xxd -r -p | md5sum
cee9a457e790cf20d4bdaa6d69f01e41  -

Se Reddit

Följ oss på Twitter: http://twitter.com/kryptera

En sårbarhet har identifierats i det förfarande som MD5 används tillsammans med signering av SSL certifikat. Genom att kombinera två äldre publika attacker:

• MD5 kollisioner
• X509 och MD5-kollisioner i dessa

Så har säkerhetsforskarna Alexander Sotirov, Jacob Appelbaum lyckats att skapa egna SSL-certifikat för godtycklig domän. De skulle exempelvis vara möjligt att skapa ett giltigt certifikat för swedbank.se med hjälp av denna attack. Dock så måste denna attack kombineras med någon annan attack mot exempelvis DNS.

We have identified a vulnerability in the Internet Public Key Infrastructure (PKI) used to issue digital certificates for secure websites. As a proof of concept we executed a practical attack scenario and successfully created a rogue Certification Authority (CA) certificate trusted by all common web browsers. This certificate allows us to impersonate any website on the Internet, including banking and e-commerce sites secured using the HTTPS protocol.

Our attack takes advantage of a weakness in the MD5 cryptographic hash function that allows the construction of different messages with the same MD5 hash. This is known as an MD5 ”collision”. Previous work on MD5 collisions between 2004 and 2007 showed that the use of this hash function in digital signatures can lead to theoretical attack scenarios. Our current work proves that at least one attack scenario can be exploited in practice, thus exposing the security infrastructure of the web to realistic threats.

HD Moore på BreakingPoint Labs har skrivit en lång och utförligt inlägg om detta: breakingpointsystems.com/community/blog/Attacking-Critical-Internet-Infrastructure.

Läs även:

MD5 considered harmful today

Creating a rogue CA certificate

Följ oss på Twitter: http://twitter.com/kryptera

Det har för några år sedan uppdagats att MD5 inte är speciellt säker att använda längre så därför satte Ronald L. Rivest igång ett arbete med att ta fram nästa generations hash-funktion nämligen MD6. Med hjälp av ett team på över 15 personer så har MD6 nu lanserats under konferensen CRYPTO ’08.

Se presentationen här:

people.csail.mit.edu/rivest/Rivest-TheMD6HashFunction.ppt

Enligt följande skriver Hal Finney om MD6:

Ron Rivest presented his (along with a dozen other people’s) new hash,
MD6, yesterday at Crypto. I am not a hash guru although I’ve implemented
SHA and its ilk many times, so I can’t guarantee all my notes are correct.
I will compare it somewhat with SHA as that is what I know.

SHA-1 is a Merkle Damgard hash, meaning that it runs a compression
function that takes as input the chaining value from the previous
compression function block, along with the next block of input, and
compresses that, creating the next chaining value for the next block.

MD6 is a tree hash, so the leaf nodes run the compression function which
takes successive blocks of input and compress it down to a chaining
value. These chaining values are then fed up to a parent node, which
uses the same compression function to produce its own chaining value,
and so on up to the root node. I think the tree branching factor was 4 -
each node has 4 children. There is also an alternative serial mode for
use by memory limited devices, but I don’t recall any details on that.

A unique feature of MD6 is that the input to the compression function is
very large – 512 bytes. SHA-1 takes 64 bytes. MD6 is oriented around 64
bit words, so this input is considered to be 64 words. The MD6 chaining
variable is 1024 bits or 16 words – compare to the hash width for the
SHA family ciphers: 160 for SHA-1, 256 or 512 for SHA-256 and SHA-512.
Per NIST’s spec, the largest hash output for SHA-3 is 512 bits, so
MD6 intentionally uses a double width chaining variable internally,
and truncates it for output.

The compression function of MD6 is particularly unusual, combining
simple steps with a large number of rounds. In SHA-1 the first thing you
do is to take the 16 32-bit input words and expand them into an 80-word
key array, each word in the expanded input being a function of certain
previous words. Then you run an unbalanced Feistel using the expanded
inputs.

MD6 starts off with something similar, using a somewhat more complex
expansion algorithm, and going on far longer. To my surprise, this is
the whole compression function! The last 16 words of this process are the
output chaining value. There is no Feistel network or any other mechanism.

In more detail, the 64 (64-bit) input words are prefixed by two sets
of about a dozen words – sorry, I don’t remember exactly how big these
were. One set is a constant value, and the other set includes a variety
of ”environmental” information about the circumstances of this instance
of the compression function. This includes global information like how
wide the hash is that will finally be derived by truncating the final
chaining value; the location of this compression function block in the
hash tree, including in particular whether we are the last (root) node;
and other such data. One notable value here is an optional per-hash key,
for creating a keyed hash, of up to 8 words (512 bits). These prepended
blocks bring the full input size up to about 87 or 89 words – again I
apologize, I am working strictly from memory here.

Now this input begins to be extended. Each additional word is a function
of about 5 of the previous 89 words. They did a search to choose the
best 5 offsets in order to maximize diffusion. The combining function
is quite simple though, composed solely of xors, ands, one right shift
and one left shift. Rivest mentioned that this made it reversible -
a desirable feature as it guarantees that no entropy is lost. At first
I was unclear how doing x = x ^ (x >> 5) for example is reversible,
for example, but then I got it. The shift amounts change each step,
again optimized by a computer search for good mixing.

But the really important point here is that there are a huge number
of such steps. The function is expressed in rounds of 16 steps
each. MD6-256 uses 104 rounds; MD6-512 uses 168. Multiply times 16 and
you are performing this extend step on the order of 2000 times. Again,
the last 16 words are the output of the compression function.

Rivest gave a lot of performance information. Because of the tree
structure, the function is highly parallellizable, and scales almost
linearly with the number of CPU cores available. With 1 core, it is not
super fast: MD6-256 on a 64-bit CPU is 77 MB/sec; MD6-512 is 49 MB/sec.
For comparison, SHA-512 is 202 MB/sec on the same setup. They need about
3 cores to match the speed of SHA-512.

He also presented a number of cryptanalytic results. There is provable
security against differential cryptanalysis, by virtue of the large number
of rounds; also security against side channels. A SAT solver and another
technique could only do something with about 11 rounds, versus the 100+
rounds in the function. The tree structure is also shown to preserve
strong properties of the compression function.

Overall it seemed very impressive. The distinctive features are the tree
structure, very wide input blocks, and the enormous number of rounds.
The cryptanalysis results were favorable. However Adi Shamir stood up
and expressed concern that his new Cube attack might apply. Rivest seemed
confident that the degree of MD6 would be several thousand, which should
be safe from Shamir’s attack, but time will tell.

Apologies again to the enormous number of authors if I have any serious
errors above. And thanks to Ron Rivest for publicizing this hash design
several months before the due date (October 31), potentially giving an
advantage to his competitotrs. He emphasized that his goal is to produce
the best possible outcome for the whole process.

Hal Finney

Följ oss på Twitter: http://twitter.com/kryptera

PHP är ett mycket väl använt programmeringsspråk som används i samband med webb-programmering. Krypteringsfunktionerna i PHP kan delas upp i följande kategorier:

• mcrypt
• openssl
• inbyggda

Här följer en mycket liten sammanställning av dessa tre kategorier:

mcrypt

Mcrypt som är ett tredjepartsbibliotek innefattar en mängd kryptering/dekrypterings-funktioner såsom:

• mcrypt_cbc — Encrypt/decrypt data in CBC mode
• mcrypt_cfb — Encrypt/decrypt data in CFB mode
• mcrypt_create_iv — Create an initialization vector (IV) from a random source
• mcrypt_decrypt — Decrypts crypttext with given parameters

Vill du exempelvis skapa en SHA256 hexsträng på godtycklig sträng kan du göra enligt följande:

$sha256b= base64_encode(bin2hex(mhash(MHASH_SHA256,$phrase)));

openssl

OpenSSL är också ett tredjepartsbibliotek och innefattar bl.a dessa funktioner:

• openssl_seal — Seal (encrypt) data
• openssl_sign — Generate signature
• openssl_verify — Verify signature

De funktioner OpenSSL tillhandahåller i PHP är mer inriktade på assymetrisk kryptering.

inbyggda funktioner

Den mest använda krypteringsfunktionen i PHP är crypt() som stödjer följande krypteringsalgoritmer:

• CRYPT_STD_DES – Standard DES-based encryption with a two character salt
• CRYPT_EXT_DES – Extended DES-based encryption with a nine character salt
• CRYPT_MD5 – MD5 encryption with a twelve character salt starting with $1$
• CRYPT_BLOWFISH – Blowfish encryption with a sixteen character salt starting with $2$ or $2a$

Övriga kryptorelaterade funktioner som återfinns som standard i PHP är exempelvis sha1 och md5.

Följ oss på Twitter: http://twitter.com/kryptera

WordPress version 2.5.1 släpps till följd av att en kryptobugg i Cookie-hanteringen gör det möjligt beräkna den HMAC som används för säkerställa att rätt användare är inloggad:

The authentication mechanism assumes that an attacker cannot calculate the HMAC. However, this assumption is broken because the two inputs used to calculate the HMAC (username and expiration) are not clearly delineated.

Läs mer om buggen här:

• http://www.cl.cam.ac.uk/~sjm217/advisories/wordpress-cookie-integrity.txt

Undrar du vad HMAC är? Förklaring enligt Wikipedia:

In cryptography, a keyed-Hash Message Authentication Code (HMAC or KHMAC), is a type of message authentication code (MAC) calculated using a specific algorithm involving a cryptographic hash function in combination with a secret key. As with any MAC, it may be used to simultaneously verify both the data integrity and the authenticity of a message. Any iterative cryptographic hash function, such as MD5 or SHA-1, may be used in the calculation of an HMAC; the resulting MAC algorithm is termed HMAC-MD5 or HMAC-SHA-1 accordingly. The cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function, on the size and quality of the key and the size of the hash output length in bits.

Följ oss på Twitter: http://twitter.com/kryptera