Measured against the field.

What. Only the devices in a conversation can read it; the servers that carry it cannot.

Why it matters. Whoever runs the servers, or breaks into them, learns nothing of what was said.

Without it. A server breach, a subpoena or a dishonest operator exposes every conversation it stored.

What. Calls between the members of a conversation, protected like its messages.

Why it matters. A call is often where the sensitive part of a conversation happens.

Without it. Calls fall back to a separate, weaker system, or to the phone network.

What. Conversations among many members, with the same protection as one to one.

Why it matters. Most real conversations involve more than two people.

Without it. Groups become the soft spot, with weaker keys or a server that can join.

What. Messages that remove themselves after a time the conversation sets.

Why it matters. A message that no longer exists cannot be leaked, stolen or compelled later.

Without it. Everything said stays on every device until someone remembers to delete it.

What. One account on a phone, a tablet and a computer at once.

Why it matters. People move between devices through the day.

Without it. Conversations live on one device only, or a second device weakens the first.

What. The handshake that agrees a shared secret resists quantum attack.

Why it matters. Traffic recorded today can be kept until a quantum computer can open it.

Without it. Every conversation recorded now is readable the day such a machine exists.

What. Identities, key exchanges and key changes are signed with a post-quantum signature; messages themselves are authenticated deniably, so a recipient can verify the sender without being able to prove it to anyone else.

Why it matters. A key exchange is only as trustworthy as the signature that vouches for it.

Without it. A quantum attacker forges a key change and steps into a conversation unnoticed.

What. A call agrees its own post-quantum key, bound to both identities, and its media keys descend from it.

Why it matters. A recorded call is as exposed to a future quantum computer as a recorded message.

Without it. Calls stay on classical keys while the messages beside them are protected.

What. No two messages are protected by the same key.

Why it matters. One exposed key then opens one message, not a stretch of the conversation.

Without it. A single key exposure reads every message it covered.

What. How often a fresh key exchange happens is the conversation's to choose.

Why it matters. The right trade between protection and battery or bandwidth differs by conversation.

Without it. Everyone gets the same fixed schedule, chosen by the vendor.

What. Every message is bound to the whole history before it, so nothing can be dropped or reordered unnoticed.

Why it matters. Silently removing or reordering messages changes what a conversation says.

Without it. A server or an attacker in the path can drop or reorder messages without a trace.

What. Key changes are published where every peer can check them.

Why it matters. A substituted key is how a third party reads a conversation while both sides believe it private.

Without it. Only a manual comparison of codes, which almost no one performs, would catch a swapped key.

What. Every change to an account's keys, settings and membership is appended to a signed, append-only chain that each device verifies before accepting it.

Why it matters. A device that accepts an unverified change can be moved to weaker settings or onto an attacker's key without anyone noticing.

Without it. A server, or anyone in the path, can roll back a protection, replay an old state or swap a key, and the device has no way to tell.

What. Every message carries two payloads of identical shape; a device of the lower tier opens one, a device of the higher tier the other.

Why it matters. A device handed over under pressure should not reveal that another view exists.

Without it. Whoever holds the device holds the whole conversation.

What. A separate code, entered under pressure, that removes the identities chosen for it and leaves the rest in place.

Why it matters. Coercion is a real threat that cryptography alone cannot answer.

Without it. The only choices under duress are to refuse or to open everything.

What. One account carries several identities with separate keys, contacts and conversations.

Why it matters. Work, family and public life need not share one identity or one contact list.

Without it. Everyone who has one identity can link it to everything else said under it.

What. A message stays the sender's after it is sent: the sender can withdraw it, set when it expires, and delete it with its keys destroyed on every device that holds it.

Why it matters. What a sender withdraws should be gone, not merely hidden from view.

Without it. A sent message belongs to every recipient's device, and deleting it removes only the sender's copy.

What. Messages are padded before they are sealed, so their length tells little, and they can pass through a relay that cannot link sender to recipient.

Why it matters. The pattern of who talks to whom, and when, reveals much even when every word is sealed.

Without it. The servers hold a complete map of every relationship and every exchange, with the size of each.

What. Each identity chooses the region that stores its encrypted records.

Why it matters. Where encrypted records sit decides which laws can reach them.

Without it. Records sit wherever the vendor put them, under that jurisdiction's rules.