Encryption; Dual Mode - Allied Telesis AR Series Hardware Reference Manual

Hardware Reference
C613-03031-01 REV C
Figure 25: Typical hardware compression ratios by file type.
Compression Ratio
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Encryption

PAC-based encryption has the following features:
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Local 32-bit processor for high speed control and data transfer.
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Dedicated high performance 32-bit Data Encryption Standard – DES and
Triple DES (3DES) – hardware.
PAC DES and triple DES encryption are based on a fast 32-bit device that
complies with FIPS PUB 46, ISO DEA-1 and ANSI X3.92 standards.

Dual Mode

Throughput of an encrypted link can be dramatically increased by using data
compression. To support this, ECPACs support both encryption and
compression, providing a dual mode that allows combined compression and
encryption operations. So that the compression phase will have the best
opportunity at finding non-random data, compression occurs before
encryption, in the order:
compression → encryption →//→ decryption → decompression
Adding compression to an encrypted link increases line throughput. Once
compression has been carried out there is less data requiring encryption,
passing back to the base system, and transferring across the network, so less
base system bus and network link bandwidth is required for a given amount of
data. This results in the dual operation being very effective where encryption is
required.
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