Item #: SCP-711
Object Class: Safe
Special Containment Procedures: Under no circumstances whatsoever is SCP-711 to be operated. Operation or attempted operation of SCP-711 is to be punished in all cases by the severest and most extreme measures available to the SCP Foundation. Enforcement of this zero-tolerance policy, should it become necessary, is to become the single highest-priority assignment for all available Foundation personnel.
The current instance of SCP-711 is to be embedded in concrete and stored in a Type 2 High-Value Item Vault at Storage Site-██, secured by at least four multiply-redundant locking systems and guarded by armed Foundation agents of no less than Level 2 security clearance. The item should never be stored in operable condition. In any major crisis during which the survival of the SCP Foundation or of any significant (>20%) portion of human civilization is called into question, the item's supervisors are to destroy it immediately and determine a safe time and place for its reassembly. No person capable of operating SCP-711 is permitted to have any knowledge of the contents of String 17 (see below).
Description: Built by the SCP Foundation from plans retrieved [DATA REDACTED], SCP-711 is a device assembled from several highly-modified [DATA REDACTED] high-energy physics equipment. Its primary function [DATA EXPUNGED]: in short, it is capable of sending data into its past and of receiving data from its future. Transmission is strictly one-way. Independent operation of the item is therefore causally impossible: any message it receives will necessarily be sent at some point in its future. All SCP-711 messages predetermine their own existence and content.
To date, exactly 17 messages have been received via SCP-711. The first string was received at 13:00 on ██/██/████ (the day of the item's creation) and sent four minutes later: it consisted only of the characters "test". With successive operations, signal quality has declined dramatically. String 1 was transmitted perfectly, reading precisely "test" both when sent and when received. String 16, when sent, also read precisely "test"; when received, it consisted of the characters "t$3s^f@" followed by 5 kB of meaningless noise. Additionally, over the course of testing, four strings were received which were never sent, and which consist demonstrably (p < 0.0001) of nothing but noise.
String 17 was detected [DATA REDACTED] ten years after the object's construction. It consists of 347 characters, either heavily encrypted or [DATA REDACTED]. Within the first fifty characters, however, is sufficient data to establish ███████████ (p █ █████) that it will be sent by a duly-authorized agent of the SCP Foundation. Its date of origin is unknown: to date, it has not yet been sent.
Since String 17 will necessarily be sent, and since it is known [DATA REDACTED] to be sent by an agent of the Foundation, the survival of the SCP Foundation and of humanity in general is guaranteed at least until such time as String 17 is transmitted. Transmission of String 17 must therefore be postponed at all costs. The above containment procedures are calculated to ensure that it will not be sent until such a time as the SCP Foundation is too weak to enforce them, in which case the Foundation will have already de facto ceased to exist.
Note: SCP-711 is an insurance policy, of sorts. Until we send String 17, we know we have to survive any crisis — otherwise that string is a BL-class predestination paradox. Once it's sent, we no longer have that guarantee. Yes, we'll have to fail at some point: we did receive String 17, after all. But the longer we postpone it, the longer we know we can survive. Stop that signal, people — our continued existence may just depend on it. — Dr. P█████████████