1# [RustCrypto]: ASN.1 DER
2
3[![Crate][crate-image]][crate-link]
4[![Docs][docs-image]][docs-link]
5[![Build Status][build-image]][build-link]
6![Apache2/MIT licensed][license-image]
7![Rust Version][rustc-image]
8[![Project Chat][chat-image]][chat-link]
9
10Pure Rust embedded-friendly implementation of the Distinguished Encoding Rules (DER)
11for Abstract Syntax Notation One (ASN.1) as described in ITU X.690.
12
13[Documentation][docs-link]
14
15## About
16
17This crate provides a `no_std`-friendly implementation of a subset of ASN.1 DER
18necessary for decoding/encoding the following cryptography-related formats
19implemented as crates maintained by the [RustCrypto] project:
20
21- [`pkcs1`]: RSA Cryptography Specifications
22- [`pkcs5`]: Password-Based Cryptography Specification
23- [`pkcs7`]: Cryptographic Message Syntax
24- [`pkcs8`]: Private-Key Information Syntax Specification
25- [`pkcs10`]: Certification Request Syntax Specification
26- [`sec1`]: Elliptic Curve Cryptography
27- [`spki`]: X.509 Subject Public Key Info
28- [`x501`]: Directory Services Types
29- [`x509`]: Public Key Infrastructure Certificate
30
31The core implementation avoids any heap usage (with convenience methods
32that allocate gated under the off-by-default `alloc` feature).
33
34The DER decoder in this crate performs checks to ensure that the input document
35is in canonical form, and will return errors if non-canonical productions are
36encountered. There is currently no way to disable these checks.
37
38### Features
39
40- Rich support for ASN.1 types used by PKCS/PKIX documents
41- Performs DER canonicalization checks at decoding time
42- `no_std` friendly: supports "heapless" usage
43- Optionally supports `alloc` and `std` if desired
44- No hard dependencies! Self-contained implementation with optional
45  integrations with the following crates, all of which are `no_std` friendly:
46  - `const-oid`: const-friendly OID implementation
47  - `pem-rfc7468`: PKCS/PKIX-flavored PEM library with constant-time decoder/encoders
48  - `time` crate: date/time library
49
50## Minimum Supported Rust Version
51
52This crate requires **Rust 1.65** at a minimum.
53
54We may change the MSRV in the future, but it will be accompanied by a minor
55version bump.
56
57## License
58
59Licensed under either of:
60
61 * [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0)
62 * [MIT license](http://opensource.org/licenses/MIT)
63
64at your option.
65
66### Contribution
67
68Unless you explicitly state otherwise, any contribution intentionally submitted
69for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
70dual licensed as above, without any additional terms or conditions.
71
72[//]: # (badges)
73
74[crate-image]: https://buildstats.info/crate/der
75[crate-link]: https://crates.io/crates/der
76[docs-image]: https://docs.rs/der/badge.svg
77[docs-link]: https://docs.rs/der/
78[build-image]: https://github.com/RustCrypto/formats/actions/workflows/der.yml/badge.svg
79[build-link]: https://github.com/RustCrypto/formats/actions/workflows/der.yml
80[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
81[rustc-image]: https://img.shields.io/badge/rustc-1.65+-blue.svg
82[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
83[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/300570-formats
84
85[//]: # (links)
86
87[RustCrypto]: https://github.com/rustcrypto
88[`pkcs1`]: https://github.com/RustCrypto/formats/tree/master/pkcs1
89[`pkcs5`]: https://github.com/RustCrypto/formats/tree/master/pkcs5
90[`pkcs7`]: https://github.com/RustCrypto/formats/tree/master/pkcs7
91[`pkcs8`]: https://github.com/RustCrypto/formats/tree/master/pkcs8
92[`pkcs10`]: https://github.com/RustCrypto/formats/tree/master/pkcs10
93[`sec1`]: https://github.com/RustCrypto/formats/tree/master/sec1
94[`spki`]: https://github.com/RustCrypto/formats/tree/master/spki
95[`x501`]: https://github.com/RustCrypto/formats/tree/master/x501
96[`x509`]: https://github.com/RustCrypto/formats/tree/master/x509
97