Specifications

ShoreTel 9.1 Page 77
SRTP-AES
Introduction
Definition
ShoreTel 9 supports SRTP for encrypting, authenticating, and replaying media streams for
ShoreGear switches and ShorePhones that support encryption. Implementation details
include the following:
• Media streams support of the AES algorithm
• ShorePhone and ShoreGear support of government certified AES
• All SRTP mandatory features:
— Support AES in Counter Mode at 128-bit
— Support key derivation rate (KDR) at 0
— Do not support AES in F8 Mode
— Do not support Master Key Identification (MKI)
Refer to the Glossary for a definition of the following terms used in this release note:
• Advanced Encryption Standard (AES)
• Real-time Transport Control Protocol (RTCP)
• Real-time Transport Protocol (RTP)
• Secure Real-Time Transport Protocol (SRTP)
• Session Description Protocol (SDP)
History
ShoreWare 6 introduced a proprietary 64-bit encryption algorithm for protecting media
streams between ShoreTel devices, including ShoreGear switches and ShorePhones.
ShoreWare encrypts RTP (payload) packets within the ShoreWare network. Call control
packets are not encrypted.
ShoreWare 8 introduced a 128-bit proprietary algorithm that replaced the 64-bit version.
Background
AES is a United States Encryption standard defined in Federal Information Processing
Standard (FIPS) 192, published in Nov. 2001. AES is a symmetric block cipher which can
process 128-bit blocks, using key sizes of 128, 192, or 256-bit.
In June 2003, the US Government announced that any key length of AES is sufficient to
protect classified information up to secret level. Top secret information requires key length
of 192 or 256-bit.
SRTP, a profile of the Realtime Transport Protocol (RTP), provides confidentiality, message
authentication, and replay protection to the RTP traffic and to the control traffic (RTCP).
AES is the default and only standardized cipher for SRTP.
ShoreTel 9 support AES and SRTP through adopting RFC 4568.