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Creating Provisioning Scripts
Open Format Configuration File
NOTE
Cisco Small Business IP Telephony Devices Provisioning Guide
File Encryption
An XML configuration profile can be encrypted by using symmetric key
encryption, whether or not it is already compressed. The supported encryption
algorithm is the American Encryption Standard (AES), using 256-bit keys, applied
in cipher block chaining mode.
Compression must precede encryption for the IP Telephony device to recognize a
compressed and encrypted XML profile. First generate the XML file, then compress
it with gzip, and finally encrypt it.
The OpenSSL encryption tool, available for download from various Internet sites,
can be used to perform the encryption. Note that support for 256-bit AES
encryption might require recompilation of the tool (to enable the AES code). The
firmware has been tested against version openssl-0.9.7c.
If the file is encrypted, the profile expects the file to have the same format as
generated by the following command:
# example encryption key = SecretPhrase1234
openssl enc –e –aes-256-cbc –k SecretPhrase1234 –in profile.xml –out
profile.cfg
# analogous invocation for a compressed xml file
openssl enc –e –aes-256-cbc –k SecretPhrase1234 –in profile.xml.gz –out
profile.cfg
A lower case –k precedes the secret key, which can be any plain text phrase and
is used to generate a random 64-bit salt. Then, in combination with the secret
specified with the –k argument, the encryption tool derives a random 128-bit initial
vector, and the actual 256-bit encryption key.
When this form of encryption is used to encrypt a configuration profile, the IP
Telephony device must be informed of the secret key value to decrypt the file. This
value is specified as a qualifier in the pertinent profile URL. The syntax is as
follows, using an explicit URL:
[--key "SecretPhrase1234"] http://prov.telco.com/path/profile.cfg
This value is programmed by using one of the Profile_Rule parameters. The key
must be preprovisioned into the unit at an earlier time. This bootstrap of the secret
key can be accomplished securely by using HTTPS.
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