This article provides us the information about the support of the Encrypted Control Link Feature on the SRX series devices.
The Encrypted Control link feature is only supported on SRX1400, SRX3400, SRX3600, SRX5400, SRX5600, SRX5800 and vSRX series. As of now, this feature is not support on the Branch Series.
For further information, please refer: Encrypted control link
For Branch series, we can configure the MAC security Feature to enable the IKE encryption on the Chassis cluster control links.
For further information, please refer: Media Access Control Security (MACsec) on Chassis Cluster