jm + transactions   9

[no title]
'For decades, the transaction concept has played a central role in
database research and development. Despite this prominence, transactional
databases today often surface much weaker models than the
classic serializable isolation guarantee—and, by default, far weaker
models than alternative,“strong but not serializable” models such as
Snapshot Isolation. Moreover, the transaction concept requires the
programmer’s involvement: should an application programmer fail
to correctly use transactions by appropriately encapsulating functionality,
even serializable transactions will expose programmers
to errors. While many errors arising from these practices may be
masked by low concurrency during normal operation, they are susceptible
to occur during periods of abnormally high concurrency. By
triggering these errors via concurrent access in a deliberate attack, a
determined adversary could systematically exploit them for gain.
In this work, we defined the problem of ACIDRain attacks and
introduced 2AD, a lightweight dynamic analysis tool that uses traces
of normal database activity to detect possible anomalous behavior
in applications. To enable 2AD, we extended Adya’s theory of weak
isolation to allow efficient reasoning over the space of all possible
concurrent executions of a set of transactions based on a concrete
history, via a new concept called an abstract history, which also
applies to API calls. We then applied 2AD analysis to twelve popular
self-hosted eCommerce applications, finding 22 vulnerabilities
spread across all but one application we tested, affecting over 50%
of eCommerce sites on the Internet today.

We believe that the magnitude and the prevalence of these vulnerabilities
to ACIDRain attacks merits a broader reconsideration of
the success of the transaction concept as employed by programmers
today, in addition to further pursuit of research in this direction.
Based on our early experiences both performing ACIDRain attacks
on self-hosted applications as well as engaging with developers, we
believe there is considerable work to be done in raising awareness
of these attacks—for example, via improved analyses and additional
2AD refinement rules (including analysis of source code to
better highlight sources of error)—and in automated methods for defending
against these attacks—for example, by synthesizing repairs
such as automated isolation level tuning and selective application
of SELECT FOR UPDATE mechanisms. Our results here—as well as
existing instances of ACIDRain attacks in the wild—suggest there
is considerable value at stake.'
databases  transactions  vulnerability  security  acidrain  peter-bailis  storage  isolation  acid 
9 weeks ago by jm
How a criminal ring defeated the secure chip-and-PIN credit cards | Ars Technica
Ingenious --
The stolen cards were still considered evidence, so the researchers couldn’t do a full tear-down or run any tests that would alter the data on the card, so they used X-ray scans to look at where the chip cards had been tampered with. They also analyzed the way the chips distributed electricity when in use and used read-only programs to see what information the cards sent to a Point of Sale (POS) terminal.

According to the paper, the fraudsters were able to perform a man-in-the-middle attack by programming a second hobbyist chip called a FUN card to accept any PIN entry, and soldering that chip onto the card’s original chip. This increased the thickness of the chip from 0.4mm to 0.7mm, "making insertion into a PoS somewhat uneasy but perfectly feasible,” the researchers write. [....]

The researchers explain that a typical EMV transaction involves three steps: card authentication, cardholder verification, and then transaction authorization. During a transaction using one of the altered cards, the original chip was allowed to respond with the card authentication as normal. Then, during card holder authentication, the POS system would ask for a user’s PIN, the thief would respond with any PIN, and the FUN card would step in and send the POS the code indicating that it was ok to proceed with the transaction because the PIN checked out. During the final transaction authentication phase, the FUN card would relay the transaction data between the POS and the original chip, sending the issuing bank an authorization request cryptogram which the card issuer uses to tell the POS system whether to accept the transaction or not.
security  chip-and-pin  hacking  pos  emv  transactions  credit-cards  debit-cards  hardware  chips  pin  fun-cards  smartcards 
october 2015 by jm
The Saga pattern
'a distribution of long-living [distributed] transactions where steps may interleave, each with associated compensating transactions providing a compensation path across databases in the occurrence of a fault that may or may not compensate the entire chain back to the originator.'
distributed  messaging  saga  patterns  architecture  transactions  distributed-transactions  distcomp 
october 2014 by jm
Aerospike's CA boast gets a thumbs-down from @aphyr
Specifically, @aerospikedb cannot offer cursor stability, repeatable read, snapshot isolation, or any flavor of serializability.
@nasav @aerospikedb At *best* you can offer Read Committed, which is not, I assert, what most people would expect from an "ACID" database.
aphyr  aerospike  availability  consistency  acid  transactions  distcomp  databases  storage 
september 2014 by jm
Scalable Atomic Visibility with RAMP Transactions
Great new distcomp protocol work from Peter Bailis et al:
We’ve developed three new algorithms—called Read Atomic Multi-Partition (RAMP) Transactions—for ensuring atomic visibility in partitioned (sharded) databases: either all of a transaction’s updates are observed, or none are. [...]

How they work: RAMP transactions allow readers and writers to proceed concurrently. Operations race, but readers autonomously detect the races and repair any non-atomic reads. The write protocol ensures readers never stall waiting for writes to arrive.

Why they scale: Clients can’t cause other clients to stall (via synchronization independence) and clients only have to contact the servers responsible for items in their transactions (via partition independence). As a consequence, there’s no mutual exclusion or synchronous coordination across servers.

The end result: RAMP transactions outperform existing approaches across a variety of workloads, and, for a workload of 95% reads, RAMP transactions scale to over 7 million ops/second on 100 servers at less than 5% overhead.
scale  synchronization  databases  distcomp  distributed  ramp  transactions  scalability  peter-bailis  protocols  sharding  concurrency  atomic  partitions 
april 2014 by jm
Non-blocking transactional atomicity
Peter Bailis with an interesting distributed-storage atomicity algorithm for performing multi-record transactional updates
algorithms  nbta  transactions  databases  storage  distcomp  distributed  atomic  coding  eventual-consistency  crdts 
september 2013 by jm
Spanner: Google's Globally-Distributed Database [PDF]

Abstract: Spanner is Google's scalable, multi-version, globally-distributed, and synchronously-replicated database. It is the first system to distribute data at global scale and support externally-consistent distributed transactions. This paper describes how Spanner is structured, its feature set, the rationale underlying various design decisions, and a novel time API that exposes clock uncertainty. This API and its implementation are critical to supporting external consistency and a variety of powerful features: non-blocking reads in the past, lock-free read-only transactions, and atomic schema changes, across all of Spanner.

To appear in:
OSDI'12: Tenth Symposium on Operating System Design and Implementation, Hollywood, CA, October, 2012.
database  distributed  google  papers  toread  pdf  scalability  distcomp  transactions  cap  consistency 
september 2012 by jm

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