The postal register’s parts, each drawn in every state it can be in. Red appears only in wax: the seal, and the word “lock”. Airmail blue marks what is open. Everything else is ink, pencil and ruling on manila.
ExampleAddresses, keys and letters here are examples made by the SDK. The Monad mainnet smoke-test key and its transaction link are real.
Six brand values and their surfaces. The wax is a state, not a decoration: it appears when a seal presses shut and when it breaks.
--bg #F3EEE3the page: envelope stock--bg-elevated #F8F4EBcards, slips, the letter--bg-sunk #ECE6D9inside the envelope--ink #1E1B16text, rules, primary buttons--muted #6E6556secondary text, labels--rule #CFC4AFregister hairlines--before #2F5D9Eopen state: a public key, a letter going out--after #A3261Eonly as wax: the seal and the word “lock”Title, Bodoni Moda 44
Address line, Bodoni Moda italic 30
Body, Public Sans 19. Plain words, like a postal form: what happened, and what to do next.
Data, IBM Plex Mono 15: 6b52 86d1 ad27 08a1 · keyOf(address)
Label capitals, Public Sans 12
Five states. It presses in 280 ms with an overshoot and cracks in 560 ms; with reduced motion the change is instant. It appears on the seal and open screens only.
An airmail edge, an italic address line, a flap that is down or folded back, a slot for the seal and one for the letter. The letter exists only before sealing and after opening.
Maya, the dentist moved to Thursday at 10:40. I will remind you on Wednesday evening.
To address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30
Epoch 1
To address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30
Epoch 1
Maya, the dentist moved to Thursday at 10:40. I will remind you on Wednesday evening.
To address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30
Epoch 1
To agent 4412
Epoch 1
The courier comes at noon.
To address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30
Epoch 1
Maya, the dentist moved to Thursday at 10:40. I will remind you on Wednesday evening.
To address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30
Epoch 1
The address line, the key as a bar strip and in hex, the epoch, and where the key was posted.
address 0xfa72da61400f345d85bf3d0d55395bdbebdb02b3
address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30
address 0x2cb6230026b0bd54a44fc92b501526e5351c7d02
address 0xd6c94ca947d4bb713647b92cea04082fe0f2078a
Ruled register columns with tabular numerals. From 1024 px up every column shows; narrower, it keeps addressee, epoch and key.
| Addressee | Epoch | Key | Posted |
|---|---|---|---|
| agent 4412Example | 1 | 862b 3bca a34d e56f | Example, not posted |
| address 0x2cb6230026b0bd54a44fc92b501526e5351c7d02Example | 2 | 895c 500f 4d5e b78b | Example, not posted |
| address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30ExampleFound by keyOf | 1 | 6b52 86d1 ad27 08a1 | Example, not posted |
| address 0xd6c94ca947d4bb713647b92cea04082fe0f2078aExample | 1 | 5930 13e0 5c26 c52f | Example, not posted |
| address 0x2cb6230026b0bd54a44fc92b501526e5351c7d02ExampleSuperseded | 1 | bf31 5c86 ef04 fff7 | Example, not posted |
| Addressee | Epoch | Key | Posted |
|---|---|---|---|
| address 0xfa72da61400f345d85bf3d0d55395bdbebdb02b3Smoke-test key: random bytes stood in for a passkey | 1 | db97 84b7 c246 deb10x35b8…e233 (the transaction that posted this key, in the explorer)block 108,289,847 | 0x35b833…1ae233 (opens the explorer)Monad mainnet · block 108,289,847 |
| Addressee | Epoch | Key | Posted |
|---|---|---|---|
| address 0x2cb6230026b0bd54a44fc92b501526e5351c7d02 | 2 | 895c 500f 4d5e b78b | Example, not posted |
| address 0x4ccacf6625c9290a533d71998a33b24cfe85fa30Found by keyOf | 1 | 6b52 86d1 ad27 08a1 | Example, not posted |
| address 0xd6c94ca947d4bb713647b92cea04082fe0f2078a | 1 | 5930 13e0 5c26 c52f | Example, not posted |
| Addressee | Epoch | Key | Posted |
|---|---|---|---|
| No keys in the register yet. | |||
A returned-to-sender slip for each SDK error a person can meet: what happened, in plain words, and what to do. Inked, never red.
Returned to sender
Your passkey provider returned no PRF output, and your encryption key is derived from that output. Some providers return none, for example Dashlane and some Chrome profiles.
What to doUse a passkey saved in a provider that returns PRF output, such as iCloud Keychain in Safari 18 or later, and create your address again.
Returned to sender
The passkey prompt was cancelled or timed out, or this device has no passkey for this site.
What to doTry again and approve the prompt. If no passkey is offered, use the device where you created your address, or one that syncs its passkeys.
Returned to sender
The directory has no key for this address, so there is nothing to seal to. Nothing was sealed and nothing was sent.
What to doAsk them to create their Letterlock address, then seal the note again.
Returned to sender
The envelope is sealed to epoch 1, and the key in hand is for epoch 2.
What to doOpen it with your passkey again: it re-derives the key for every earlier epoch, including epoch 1.
Returned to sender
The envelope did not open. It names key 6b52 86d1 ad27 08a1, and the passkey you chose derives 5930 13e0 5c26 c52f.
What to doOpen it again and choose the passkey you used when you created this address.
Returned to sender
The envelope failed its authentication check: it was changed after it was sealed. No part of it was decrypted.
What to doDon’t trust this copy. If you know who sent it, ask them to seal the note again.
Returned to sender
Posting is a Monad transaction, paid in MON by your passkey account, and it holds too little. Nothing was sent.
What to doSend a little MON to your passkey account from any wallet, then press the button again.
Returned to sender
Monad’s RPC gave no answer, so nothing is known either way. This is not the same as “no key”: the key may well be there.
What to doTry again in a moment. If a transaction link was shown, open it before sending anything again.
Returned to sender
Only the account that owns an ERC-8004 agent in the identity registry may post that agent’s key, and this account does not own it.
What to doPost the key from the account that owns the agent, or check the agent id.
ExampleThe quoted keys and epochs are what the SDK’s open() really reports for example letters: Maya’s letter opened with Nadia’s passkey, and Kai’s epoch 1 letter with his epoch 2 key.
Ink marks struck on the paper. The strip is a postal 4-state bar code of the key fingerprint: 32 bars, two bits each, the same 16 digits as the hex beside it.
Postmarkring onlyPostmarkwith cancellation barsWordmarkoutlined; “lock” is wax6b52 86d1 ad27 08a1KeyStripopen: a key found in the registerKeyStripink · pencil (superseded)ExampleBadgestamped on anything not on chainA postal form’s lines: capitals for the label, a ruled box to write in. The note is written on a ruled sheet and counted in bytes, the unit the envelope limit is written in.
An address (0x…) or an agent (agent:<id>).
TextFieldaddress, in the data faceThat is not a whole address: an address is 0x and 40 hex digits.
TextFieldwith a form error85 bytes
NoteFieldbytes counted live85 bytes of 64 bytes
The note is over its limit of 64 bytes.
NoteFieldover its byte limit (64 here), announced once as it goes over