Resilio Sync Key Official

In the world of peer-to-peer (P2P) file sharing, the Resilio Sync key

(formerly known as a "secret") is the digital DNA of a shared folder. Unlike cloud services that rely on centralized accounts and servers, Resilio Sync uses these alphanumeric strings to identify, secure, and connect devices directly to one another. The Evolution of the Key

The structure of a Resilio Sync key has evolved to support different security and functionality needs. You can typically identify a key's purpose by its first character: Read-Write (Starts with A or D):

Grants full bidirectional synchronization. Peers with this key can view, download, and modify files, with changes syncing back to all other devices. Read-Only (Starts with B or E):

Allows a device to download and receive updates but prevents any local changes from being uploaded to the rest of the mesh. Encrypted (Starts with F):

Designed for "untrusted" devices (like a third-party server). This key allows a peer to store and help distribute data without being able to decrypt or view the actual file contents. One-Time (Starts with C):

Temporary keys used for single-use sharing or specific session setups. How the Key Works (The Flow)

When you generate a Read-Write key for a folder, Resilio Sync creates a complex cryptographic chain: Identity Generation: resilio sync key

It builds a pair of asymmetric keys to sign and verify file hashes. Derived Keys:

From the master RW key, it automatically generates the Read-Only key and a unique Share ID. Discovery:

Once you share a key, peers use it to find each other via trackers, DHT, or local discovery. Encryption:

A separate traffic encryption key is generated for every session, ensuring that data in transit is protected by AES-128 encryption. Practical Application: "Sync Stories"

Users often leverage these keys to bypass the limitations of the "cloud": Personal Backups:

A photographer might use a Read-Write key to sync their "Photos" folder between a laptop and a home NAS, ensuring every edit is instantly backed up without paying for storage. Selective Sharing:

A business might give a "Sales" team a Read-Only key for a price-list folder, ensuring everyone has the latest data but nobody can accidentally delete it. Large File Distribution: In the world of peer-to-peer (P2P) file sharing,

Video producers use keys to send multi-gigabyte raw footage directly to editors, hitting speeds up to 10 Gbps on optimized networks. Fast, Unlimited, and Cheap File Sharing: Resilio Sync

Resilio Sync (formerly BitTorrent Sync), a (also called a "secret") is a unique string of characters used to identify and connect shared folders across different devices without using cloud storage. How Resilio Sync Keys Work

: Keys consist of capital letters (A–Z) and numbers (2–7). The first character typically indicates the folder type or permission level. : Data is encrypted using

keys derived from these secrets. Sharing the key effectively shares access to the folder. Peer-to-Peer

: Once a key is entered on a second device, it uses that key to find other "peers" (devices) with the same folder and begins a direct transfer. Types of Folder Keys

There are three primary types of keys used for folder sharing: Read/Write

: Allows devices to both upload and download changes. Any file modified on one device will update on all others. copy the data into it

: Allows a device to receive updates but prevents any local changes from syncing back to the other peers.

: Used for "untrusted" nodes (like a VPS). This key allows a device to store and help distribute files without being able to actually read or decrypt the data. Handmade Network License vs. Sync Keys It is important to distinguish between folder keys and license keys

6. Operational Lifecycle

[Create Folder] → Generate Full Key K
                         ↓
              [Share K out-of-band]
                         ↓
   Peer B enters K → DHT lookup → Connect to Peer A
                         ↓
              Sync all data encrypted
                         ↓
   Optional: Generate Read-Only key from K → share with read-only users

Decentralized Content Addressing & Peer Authentication

Quick action steps

If you need to share: generate appropriate key in Resilio Sync UI and send it securely.
If key leaked: remove peer access on origin device and generate a new secret.
For backups to untrusted host: use encrypted/one-way key.

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1. Full Access Key (Read & Write)

This is the "master key."

Permissions: Users can view, add, modify, and delete files. Any change made by any peer is propagated to all other peers.
Use Case: Team collaboration, syncing your own documents between your work PC and home laptop, or family photo albums.
Risk: High. If this key leaks, a malicious actor can delete all your data across all connected devices.

Case 3: The Data Hoarder

A user has a 10TB media library at home but a 500GB SSD on their laptop.

Solution: Use Selective Sync. The user shares the library via a Full Access key to the laptop but does not sync everything. The key allows the laptop to browse the file list (only file names, not content) and download specific files on demand.

Resilio Sync Key vs. Modern Alternatives

How to Mitigate Risks

Use Read Only Keys for Distribution: When sharing with semi-trusted parties, always use a Read Only key.
Regenerate Keys: If a key is compromised, you cannot "revoke" it. You must create a new folder, copy the data into it, share the new key, and ask all legitimate users to switch.
Predefined Hosts: For enterprise use, disable the Global DHT and Tracker discovery. Only connect via "Predefined Hosts" (manual IP entry). This makes the key useless without knowing the specific IP addresses of your peers.