Taggad: ECDSA

iOS-kryptering

Kryptering i Apple iOS: iMessage, AirPlay och AirDrop

Apple har nu släppt ett dokument som beskriver säkerheten i operativsystemet iOS. Detta dokument är omfattande och är på hela 33 sidor.

I dokumentet beskriver bl.a. att iOS använder sig  av ARM-processorns funktion vid namn Execute Never (XN) för att markera pages som icke exekverbara. Även så använder Safari webbläsaren denna för sin JavaScript JIT-kompilerare. Detta för att försvåra exploitering.

iMessage kryptering

Apple avänder sig av DJB:s Curve25519 (ECDH) samt RSA och AES en hel del, exempelvis för iMessage-kryptering:

When a user turns on iMessage, the device generates two pairs of keys for use with the service: an RSA 1280-bit key for encryption and an ECDSA 256-bit key for signing.

AirPlay kryptering

Även hur AirPlay använder kryptering beskrivs:

AirPlay audio and video streams utilize the MFi-SAP (Secure Association Protocol), which encrypts communication between the accessory and device using ECDH key exchange (Curve25519) with 2048-bit RSA keys and AES-128 in CTR mode

AirDrop kryptering

När en användare slår på AirDrop så skapas en 2048-bit RSA-nyckel som sedan används för TLS-kommunikation över Bluetooth Low-Energy (BTLE) eller WiFi. Ingen accesspunkt eller Internetanslutning behövs för att använda AirDrop. Verifiering av vem som skickar genomförs genom kontroll mot kontaktlistan ”Contacts Only”.

iOS Security

Page 3 Introduction
Page 4 System Security
Secure Boot Chain
System Software Authorization
Secure Enclave
Touch ID
Page 8 Encryption and Data Protection
Hardware Security Features
File Data Protection
Passcodes
Data Protection Classes
Keychain Data Protection
Keybags
FIPS 140-2
Page 14 App Security
App Code Signing
Runtime Process Security
Data Protection in Apps
Accessories
Page 17 Network Security
SSL, TLS
VPN
Wi-Fi
Bluetooth
Single Sign-on
AirDrop Security
Page 20 Internet Services
iMessage
FaceTime
Siri
iCloud
iCloud Keychain
Page 27 Device Controls
Passcode Protection
Configuration Enforcement
Mobile Device Management (MDM)
Apple Configurator
Device Restrictions
Supervised Only Restrictions
Remote Wipe

Dokumentet kan du ladda hem här:

Kryptouppdateringar i Microsoft Windows

Windows krypteringMicrosoft meddelade för ett tag sedan att man avser att stärka krypteringen i Windows under perioden 2012-2013 och nedan kan du se några av förbättringarna som håller på att införas.

Många av dessa förändringar är redan inbyggda i Windows 8 samt Windows Server 2012 och är även nu åtgärdade för att fungera på äldre operativsystem.

Generellt så gäller förändringarna vilka krypteringsalgoritmer som används men även längden på nycklar.

Microsoft Security Advisory 2661254
This update set a mandatory key length for RSA keys of 1024 bits or stronger by restricting the use of certificates with RSA keys less than 1024 bits in length.

Microsoft Security Advisory 2813430
This update establishes functionality that enables consumers to update trusted and disallowed Certificate Trust Lists (CTL) in non-internet connected environments. CTL’s are a list of approved hashes or certificates approved by a trusted third party. This update allows customers more control in which parties they trust.

Microsoft Security Advisory 2862966
This update established a framework for managing asymmetric cryptography by adding features for monitoring and directly controlling which cryptographic algorithms are used (RSA, DSA or ECDSA), options to set minimum key length as well as to set which hashing algorithms will be permitted for code signing and other functions. All functionality is documented in detail on Microsoft TechNet.

Microsoft Security Advisory 2862973
This update released today as Downloadable Content (DLC) gives customers the option to restrict the use of certificates that utilize the MD5 hashing algorithm as part of their digital signature. We recommend that customers download and test the update in their environment at the earliest opportunity, this will be especially useful for environments that have little or no inventory of their cryptographic and certificate dependencies. This update will only affect MD5 as used in server authentication, code signing and time stamping. There are exceptions for certain certificates and timestamps, please see KB 2862973 for additional details. Microsoft is planning to release this update through Windows Update on February 11, 2014 after customers have a chance to assess the impact of this update and take necessary actions in their enterprise.

Sårbarhet i OpenSSL:s ECDSA-implementation

En ny tidsattack (timing attack) har uppdagats i OpenSSL:s implementation av Elliptic Curve Digital Signature Algorithm (ECDSA). Med hjälp av denna attack så är det möjligt att läsa ut den privata nyckeln via exempelvis protokollet TLS. Sårbarheten hittades av Billy Bob Brumley och Nicola Tuveri:

”For over two decades, timing attacks have been an active area of research within applied cryptography. These attacks exploit cryptosystem or protocol implementations that do not run in constant time. When implementing an elliptic curve cryptosystem that provides side-channel resistance, the scalar multiplication routine is a critical component. In such instances, one attractive method often suggested in the literature is Montgomery’s ladder that performs a fixed sequence of curve and field operations.

This paper describes a timing attack vulnerability in OpenSSL’s ladder implementation for curves over binary fields. We use this vulnerability to steal the private key of a TLS server where the server authenticates with ECDSA signatures. Using the timing of the exchanged messages, the messages themselves, and the signatures, we mount a lattice attack that recovers the private key.”

Läs även:

Remote Timing Attacks are Still Practical:
http://eprint.iacr.org/2011/232.pdf