dat 0.4.0

# DAT - Data Access Token

# Cargo.toml
```
dat = { version = "0.4.0" }
```

# DAT Format
> ```expire```.```kid```.```plain```.```secure```.```sign```

- ```expire```: number
  - Unix-Timestamp (sec)
- ```kid```: stringifiable
  - Keystore(sign and crypt) ID
- ```plain```: base64 url no pad
  - Text Data 
- ```secure```: base64 url no pad
  - Encrypted Text Data
- ```sign```: base64 url no pad
  - Keystore\[kid\].sign(expire.kid.plain.secure.)

# Keystore Format
```
// example
1.123.P256.Qb40YzdR3QbRG_oh4QgZrBdrhzaFqFzah5Y4o4jE0js.AES128GCMN.ZCJk5cJNR6lrsMEuRRHWuQ.1775801019.1775861119.600

// format
version.kid.signAlg.signKey.cryptAlg.cryptKey.issueBegin.issueEnd.tokenTtl

// format description
version: keystore format version
kid: keystore id,
signAlg: sign algorithm,
signKey: keystore sign key data (base64 url no pad),
cryptAlg: crypt algorithm,
cryptKey: keystore crypt key data (base64 url no pad),
issueBegin: issue begin time (unix timestamp secs),
issueEnd: issue end time (unix timestamp secs),
tokenTtl: token TTL (secs)
```

## support sign – verify algorithm
| name   | algorithm  |
|--------|------------|
| P256   | secp256r1  |
| P384   | secp384r1  |
| P521   | secp521r1  |

## support crypt algorithm
| name       | algorithm                   |
|------------|-----------------------------|
| AES128GCMN | aes-128-gcm n(nonce + body) |
| AES256GCMN | aes-256-cbc n(nonce + body) |