SHAPING THE FUTURE OF SATELLITE COMMUNICATIONS
• Encrypted content key: There are two encrypted content keys per stream - the
odd encrypted content key and the even encrypted content key. These keys are
entered by the user through any interface and used to compute the
corresponding content key which is stored in the device. Encrypted content
keys cannot be read back on any interface.
• Content key: There are two content keys per stream - the odd content key and
the even content key. The content keys are entered by the user through any
interface or these keys are computed from the corresponding encrypted content
key. Content keys cannot be read back on any interface.
• Key decryptor: The key decryptor is an AES decryption engine used to
compute the content key based on the encrypted content key and using the
group key as the AES key. The previous statement is only valid for 128-bit keys.
In case of 64-bit keys, a DES decryption engine is used instead of AES.
• Odd/Even key: The operator on the modulator selects which key to use. The
demodulators automatically detect which key is used (odd or even) and selects
the key of the same type (odd or even) to performing the decryption.
9.13.2.3 Key Sizes
The key management layer for AES is defined to work with two key sizes: 128 bits
for maximum security and 64 bits for meeting exportation restrictions in some
countries - the 64 bit keys have a randomness of 56 bits to fully meet exportation
restrictions. The last byte of the key is not used.
It is possible that the security mode on your modulator is restricted in the factory to
use 64-bit keys only. In that case, you cannot switch to 128-bit key mode.
EL170/470/970 >> Unit >> Control >> AES
Figure 116 - Group Key Field
Switching from one key size to another erases all keys in use.
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