The Cryptographic Sequencer was a device that allowed Batman to bypass security consoles, track signals, and listen in on radio broadcasts. The device was originally created to disable the security gates on Arkham Island. The security protocols used for disabling these gates were developed by Wayne Enterprises, being a two-part biometric sequence, with one part that was given to Warden Sharp.
Arkham Origins Incident
Resembling a miniature computer, Batman utilized that to remotely hack into nearby computer terminals and door controls. It could also be used to intercept, decode, and listen to various radio frequencies.
Arkham Asylum Incident
During the Joker's takeover of Arkham Asylum, Warden Sharp's terminal for his part of the sequence was destroyed. Upon learning this, Batman took Sharp's own part of the biometric sequence and replaced Sharp's destroyed terminal with his own, and created a fully-functional Cryptographic Sequencer, which he used to disable the security gates around the Asylum, that allowed him access to areas that were otherwise inaccessible to him. That helped Batman get to areas such as Killer Croc's Lair in the Sewers as well as activating panels. Some panels were rigged with Smilex gas canisters (Those panels usually had two or three locks to unlock). If the player took too long to crack a security lock on a rigged panel, Joker gas would be pumped into the room.
Arkham City Incident
Sometime after the events that followed Joker's takeover of Arkham Asylum, Batman upgraded this item to the Cryptographic Sequencer V2, which was used to listen in on radio broadcasts and track signals to new radio frequencies once certain radio chips were added. In contrast to the previous Cryptographic Sequencer, the Cryptographic Sequencer V2 unlocked security panels by entering a certain code instead of a wave frequency. That also came in useful when Batman was able to crack certain codes once he downloaded the Gotham City Municipal Codes from the old GCPD Building, which allowed him access to the main areas of Arkham City.
During his attempt to hack into the security panels in the Museum, Batman discovered that Penguin ha placed military grade communication jammers around his territory to block all communication, which prevented Batman from using his Cryptographic Sequencer and required him to destroy the jammers, so he could get into the Museum.
After Batman downloaded the TYGER Master Control Program from a TYGER Helicopter, he was able to hack into the TYGER security panels as well.
Batman could also listen in on Penguin's channel, Puffin Zero via an encryption key from one of Penguin's Henchmen as well as the TYGER frequency by using an encryption key that he stole from a TYGER operative. He could also listen to the Gotham City Radio broadcasts. It was also used to crack security panels that controlled various doors and traps, which featured much more prominently with Riddler Trophies and Riddler Rooms.
Arkham Knight Incident
The Cryptographic Sequencer was replaced with a new tool fresh off of the WayneTech R&D, called the Remote Hacking Device, which did what the Cryptographic Sequencer did and more, like being able to hack and control enemy drones, while also being small enough to fit in Batman's palm, and negated the need to stop and work the device. However, it lacked the Cryptographic ability to monitor radio frequencies.
The Cryptographic Sequencer could be upgraded to be better. It could be upgraded to be more powerful, and thus allow easier and quicker code breaking. It could also be upgraded to have the waves more amplified, so that codes could be broken from further away, such as being blocked by a barred door or the security gate that it powered.
- An oversight by the developers was that many gadgets, including the Cryptographic Sequencer, were more advanced in Arkham Origins than in previous games. However, Arkham Origins chronologically took place before the other games' stories, leading to confusion over Batman's arsenal development. However, it might be that the gadget that Batman used in Arkham City was possibly the exact same gadget that he used in Arkham Origins, instead of an upgraded version of the machine that he acquired in Arkham Asylum. It's possible that Batman simply didn't take it with him since he was going to stop the Joker at the Mayor's office and wasn't expecting a hostile takeover of Arkham Asylum and the Asylum had different security measures.
- In Arkham City, Batman could intercept hidden radio messages from Scarecrow with the Cryptographic Sequencer, likely created as hints towards the succeeding game, Arkham Knight.
- Find the coordinates X700.00, Y490.00 on the Sequencer to intercept a radio frequency that contains the following repeating numbers: 9, 23, 9, 12, 12, 18, 5, 20, 21, 18, 14, 2, 1, 20, 13, 1, 14. The cypher is a simple 123 = abc etc. The message is decoded as "I WILL RETURN BATMAN."
- Find the coordinates X500.00, Y900.00 on the Sequencer to intercept a radio frequency that contains the following repeating numbers: 5, 15, 9, 7, 21, 18, 18, 14, 3, 5, 24, 15, 12, 7, 22, 3, 10, 5, 15, 9, 22, 3, 8, 25, 26, 15, 16, 25, 10, 15, 17, 25. The cypher is 123456=cbazyx, with the other letters continuing in reverse order. The message is decoded as "YOU WILL PAY FOR WHAT YOU HAVE DONE TO ME."
- Find the coordinates X200.00, Y500.00 on the Sequencer to intercept a radio frequency that contains the following repeating numbers: 3, 20, 26, 18, 26, 16, 24, 1, 11, 4, 24, 9, 3, 8, 5, 2, 12, 18, 6, 16, 7, 11, 3, 10, 17, 5, 13, 4, 21, 8. Decoding this message is more complicated. First, match each number to its corresponding letter in the alphabet (A=1, B=2, C=3, etc.). This gives the sequence: C T Z R Z P X A K D X I C H E B L R F P G K C J Q E M D U H. Using an Atbash cipher, A is substituted for Z, Y for B, X for C, and so on. This gives the sequence: X G A I A K C Z P W C R X S V Y O I U K T P X Q J V N W F S. Finally, a Vigenere cipher is used. A keyword is needed to solve the cipher, and the keyword for the code is "SCARECROW". Once decoded, it reads: "FEAR WILL TEAR GOTHAM CITY TO SHREDS."