eNot — Encoding Notations

eNot (Encoding Notations) is a JSON-driven templating engine that serializes structured data into binary formats — primarily ASN.1 DER, with BER-TLV support showing the design is not limited to a single format.

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The problem it solves

Whenever an application needs to produce structured binary data — network protocols, smart-card commands, certificate fields, device provisioning payloads — the choices are usually the same: reach for a heavy framework that makes all the structural decisions for you, or write low-level encoding code that is brittle, hard to review, and even harder to reuse across projects.

eNot takes a different approach. The binary structure is described as a plain JSON template:

{
  "type": "asn.1",
  "attributes": { "tag": "utf8_string" },
  "body": "${common_name}"
}

At serialization time you supply the values:

Enot enot = new Enot(registry, objectMapper);
List<byte[]> der = enot.serialize(templateJson,
        new SerializationContext.Builder(objectMapper)
                .withParam("common_name", "Alice")
                .build());

That's it. The engine resolves ${common_name}, encodes the UTF-8 string as DER, and returns the bytes. No hard-coded structures, no framework lock-in.

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Going further — loops, conditions, and composition

Binary structures are rarely flat. eNot handles this with built-in control-flow elements.

Loops iterate over an array of parameters and produce one encoded element per entry — any repeated structure maps directly to a loop:

{
  "type": "system",
  "attributes": { "kind": "loop", "items_name": "dns_name" },
  "body": {
    "type": "asn.1",
    "attributes": { "tag": "tagged_object", "implicit": 2 },
    "body": {
      "type": "asn.1",
      "attributes": { "tag": "ia5_string" },
      "body": "${value}"
    }
  }
}

Conditions encode a body only when an expression evaluates to true. The body is simply skipped when the expression is false, so a single template can cover multiple encoding variants depending on the input. One example is encoding a date in a different format depending on its value (as RFC 5280 requires for X.509 validity dates):

{
  "type": "system",
  "attributes": {
    "kind": "condition",
    "expression": "${expires_on} < '2050-01-01T00:00:00Z'"
  },
  "body": {
    "type": "asn.1",
    "attributes": { "tag": "utc_time" },
    "body": "${expires_on}"
  }
}

References let one template include another by identifier at parse time, so large or complex structures are assembled from smaller, independently testable pieces rather than one monolithic file — the same composability principle that makes software maintainable applies directly to binary templates.

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Why templates in JSON?

The format was a deliberate choice:

• Templates are plain text — version-controlled, diff-able, reviewable in a pull request
• The structure mirrors the binary output — a sequence wrapping a set wrapping a utf8_string is exactly how it looks in the JSON tree
• The engine is format-agnostic — the same parser and serializer infrastructure drives both the asn.1 and ber-tlv type systems; new formats plug in via EnotRegistry
• Placeholder resolution, condition evaluation, and loop iteration are all handled by the engine, not scattered across application code

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Status

eNot is not yet published to Maven Central. Build locally first:

mvn install

Then reference the snapshot version (see Quick Start).

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Modules

Module	Description
core	Parser, serializer, expression engine, type registry
ber-tlv	BER-TLV type extension — proof that the engine is not tied to ASN.1

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Building

Requirements: Java 17+, Maven 3.8+

mvn install          # build and run all tests
mvn -pl core test    # run only core module tests

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Documentation

Document	Description
Quick Start	Dependency, first template, serialization
Format overview	Element structure, values, placeholders, scoping
ASN.1 elements	All tags and accepted body types
System elements	loop, condition, group, reference, bit_map, sha1, …
Expression syntax	Operators, functions, type rules

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License

Apache License 2.0 — see LICENSE.