To be honest, we don't know by what meta loader (metldr) is encrypted. ERK (EID Root Key) is first 48 bytes of this file. But outside PS3, no one yet decrypt it, so no one retrieved ERK without working PS3. Maybe it is encrypted by some info from SysCon? Who knows. @zecoxao
You have missed the train. Obtaining this key on CFW is few seconds of effort (on HEN not yet possible).