The document discusses cryptographic processes related to key generation and encryption in Bluetooth communication, highlighting key concepts such as link keys, master/slave relationships, and the constraints on encryption mechanisms. It outlines various algorithms utilized in encryption, including block and stream ciphers, and the transformations of key lengths. Specific operations like kinit and kc derive key values for secure pairing and communication between devices.

1. Higher
Layer_Key
Est
User
Interaction
(PIN)
Pre-Config
Pkey
Init Key
“Kinit”
Old Link
Key
Link Key
Authentication
Process
Overlay
Key
Encryption
Key
Constraint
Key
Payload
Key “KP”
Encryption
Process
Shared Secret b/w
2x comm devices
Kinit = E22(Pkey, IN_RAND, LPKey)
Short-lived key, used for pairing
Shared secret,
used after pairing
Kovl = E22(K, RAND3, 16)
Conveying the master key to each
of the slave via Broadcast data
Derived from Link key as:
Kc=E3(K,EN_RAND,COF)
Used for encryption in USA
Impose restrictions on the export of encryption mech
Conversion of 128 bits Kc into a Kc’ (length < 128 bits)
E22 E21
AC0
E0
E3
Summary of Algorithms
• E1, E3, E21, E22 use SAFER+ (Block Cipher)
• E0 is based on Stream Cipher
• 128 bits block cipher
• Key is directly input to E0 to generate a
stream for Encryption
Actual key used to Encrypt/ Decrypt B.T packets
Kp=E0(KC’, CK_VAL, BD_ADDR, EN_RAND)
BLUETOOTH - KEY HIERARCHY
OR
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g1
L & g2
L