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Security Issues in Wireless Video

encryption data content devices

Definition: Security issues in wireless video systems include viruses, malicious attacks, and denial of service .

Video has been or is expected to be widely used by mobile devices and transmitted over wireless networks such as cellular networks for mobile phones and Wireless Local Area Networks (WLANs) for eHomes. Wireless video services include video downloading, streaming, and conferencing. Users in a wireless network communication with each other through the open air that unauthorized users can intercept content transmissions or attackers can inject malicious content or penetrate the network and impersonate legitimate users. This intrinsic nature of wireless networks has several specific security implications. Sensitive and valuable video content must be encrypted to safeguard confidentiality and integrity of the content and prevent unauthorized consumption. Wireless enables mobility which requires small form factors. Therefore a wireless video device is easily lost or stolen, adding additional security requirement to prevent somebody from gaining access to confidential information in or through the device. A mobile device and its user must be authenticated before a wireless video service. The private information such as what video content is downloaded or viewed, the device’s location, etc. should also be protected. Most of the security issues in wired video systems such as viruses, malicious attacks, denial of service, are equally applicable to wireless video systems.

The security implications of wireless video have a great impact on the design of such a system. A wireless device has limited memory and computing power. Battery capacity is also at a premium. Growth in battery capacity has already lagged far behind the increase of energy requirement in a wireless device. The security concerns mentioned above make it even worse since security processing has to take away some of the premium computing resources and battery life. Security processing generally applies asymmetric encryption such as RSA or Elliptic Curve Cryptosystem (ECC) for authentication and key management, symmetric encryption such as Advanced Encryption Standard (AES) for data encryption, and the Secure Hash Algorithm (SHA)-1 for integrity checking, and a random sequence generator to generate random numbers. Some of those operations are expensive. For example, when a Toshiba Satellite 1200 laptop transmits a 5MB file, encryption with AES of 128 bits would increase battery consumption by 75% and time consumption by 65% as compared to the case without encryption. Asymmetric encryption is even worse. To make things worse, a wireless device is often required to execute multiple security protocols at different network layers. Compared to wired networks, a wireless network has certain unique features: wireless communications have poor channel quality and are prone to errors, have limited and fluctuating bandwidths. All those issues have to be carefully considered and balanced in designing a wireless video system.

There are several technologies proposed to address the above issues in wireless video. Typical ones include:

  1. Lightweight cryptographic algorithms and encryption schemes. Due to low processing power and premium battery life, low complexity cryptographic algorithms are used for wireless devices. For example, ECC uses much shorter keys than RSA for the same level of security, resulting in more efficient asymmetric encryption. This feature makes ECC highly suitable for small wireless devices. Video encryption can also be lightweight. For example, selective encryption can be used to encrypt only important video data instead of the whole data, dramatically reducing the amount of data to be encrypted or decrypted.
  2. Security processing instructions and chips. Security operations can be executed more efficiently if a general purpose processor supports certain security and multimedia related instructions. Many embedded processors used for wireless devices have already extended to include basic cryptographic instructions. For example, SecureCore processors have added cryptographic instructions to speed up secure data processing. An independent security coprocessor or chip completely devoted to security processing is also a viable approach.
  3. Scalable protocols. Wireless devices may have a large range of capacities, from powerful laptops to small handset devices. A security protocol designed for wireless systems must be scalable that different wireless devices can apply a subset of the protocol that matches its capability. The Open Mobile Alliance (OMA) has adopted Digital Rights Management (DRM) specifications for portable devices that support three different modes for different devices and applications: forward lock which prevents the content from leaving the destination device; combined delivery which adds digital rights definition to the content; and separate delivery which offers content encryption an supports super distribution.
  4. Scalable coding and encryption. The bandwidth of a wireless network fluctuates greatly. Wireless devices have a great variety of display characteristics, from a full screen in a laptop to a tin screen in a cellular phone. Video content should be in a format that is well adapted to the dynamic nature of wireless networks, and different display characteristics. Scalable coding and encryption have been proposed to serve the purpose. A scalable vide coding such as MPEG-4 Fine Granularity Scalability (FGS) encodes video content into a small non-scalable base layer and scalable enhancement layers. Data in the enhancement layer can be dropped during bandwidth fluctuation. Scalable encryption such as the scheme in enables FGS in encrypted codestream so that encrypted video data can be adapted without decryption. No secret key is therefore needed to perform a truncation of encrypted data to fit the current bandwidth.
  5. Error resilience. Video data when transmitting over wireless networks must be organized to be error resilience to prevent extensive visual degradation when errors occur. For example, data for wireless networks should be packetized into small packets so that errors in a packet or loss of a packet affect a small amount of data. Error resilience technologies such as placing resynchronization markers periodically are also used to stop error propagation.
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