CredentialsWithAttachments.md

Credential with attachments

Credentials with attachments can be issued and attachments can be shown in client application.

Let's consider an example how attachments can be implemented as base64 encoded values.

NOTE: base64 encoded strings is just a representation of attachment, any other ways are valid and up to your system architecture.

Assume that attachments will be implemented the next way:

• Attachments should be added in form of base64 encoded string.
• Photo, audio, video and other common documents can be attached to a credential and supported in client application.
• Credential field name must have _link postfix to be treated as an attachment by the application.
• All supported types are listed in Supported mime types section.

Issuing credentials with attachments

NOTE: for general credential messages structure see Credentials section.

To use attachment field in credential the next JSON string will be used as value in credential attributes list:

{
  "mime-type": "image/png",
  "extension": "png",
  "name": "my_photo.png",
  "data": {
    "base64": "BASE_64_ENCODED_STRING"
  }
}

mime-type, extension and name should be filled with file name, its extension and mime type. Please refer to Supported mime types section to find examples of mime types which can be supported in client application. data field should contain JSON object which has base64 field. Attached file should be encoded as base64 string and this string should be used and base64 field's value.

Also to mark field as an attachment, _link postfix must be added to credential field name.

So credential attributes in credential_attrs field should look like this

{
  "First Name": "Amy",
  "Last Name": "Reeders",
  "Photo_link": "{\"mime-type\": \"image/png\", \"extenstion\": \"png\", \"name\": \"my_photo.png\", \"data\": {\"base64\":\"data:image/png;base64....\"}}"
}

Requesting field with attachment in proof request

NOTE: for proof request messages structure see Proofs section

To request a credential with an attachment, field name with _link postfix should be used in proof request attributes. So requested attributes will look like this

"requested_attributes": {
  "First Name": {
    "name": "First Name"
  },
  "Last Name": {
    "name": "Last Name"
  },
  "Photo": {
    "name": "Photo_link"
  },
}

Supported mime types

• Photo types:
  • image/jpeg
  • image/png
  • image/jpg
• MS Word types:
  • application/msword
• MS Excel types:
  • application/vnd.ms-excel
• MS CSV types:
  • text/csv
• MS Powerpoint types:
  • application/vnd.ms-powerpoint
• PDF types:
  • application/pdf
• Audio and video types:
  • audio/mp4
  • audio/mpeg
  • audio/mp3
  • video/mp4

Limitation

There is a limitation in ~400KB of the maximum allowed size for Credential Values that can be processed.