Support loading keys from Polkadot-JS accounts. (#1661)

* Import key pair from JSON.

* Get secret.

* Fix JSON decryption.

* Fix error handling.

* Fix warnings.

* Add polkadot-js links.

* Fix packages.

* Fix json feature.

* Add copyright message.

* Update Cargo.toml

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

* Improve error handling.

* Expect that provided parameters are valid.

* Add Scrypt parameters comment from JS implementation.

* Fix expect() message

* Make from_ed25519_bytes() pub(crate)

* Rename json feature to polkadot-js-compat

* Add comment about polkadot-js-compat dependencies.

Co-authored-by: James Wilson <james@jsdw.me>

* Add decrypt_json() public method.

* json.rs -> polkadot_js_compat.rs

* Simplify JSON structs.

* Only declare from_ed25519_bytes() with polkadot-js-compat

* Move decrypt_json() to top of file.

* Don't enable new crates on std feature

* Avoid enabling a couple of existing optional crates on std feature

---------

Co-authored-by: Jonathan Brown <jbrown@acuity.network>
Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>
Co-authored-by: James Wilson <james@jsdw.me>

Cargo.lock

@@ -541,9 +541,9 @@ checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
 
 [[package]]
 name = "base64"
-version = "0.22.0"
+version = "0.22.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9475866fec1451be56a3c2400fd081ff546538961565ccb5b7142cbd22bc7a51"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
 
 [[package]]
 name = "base64ct"
@@ -853,6 +853,7 @@ checksum = "773f3b9af64447d2ce9850330c473515014aa235e6a783b02db81ff39e4a3dad"
 dependencies = [
  "crypto-common",
  "inout",
+ "zeroize",
 ]
 
 [[package]]
@@ -1174,6 +1175,21 @@ dependencies = [
  "subtle",
 ]
 
+[[package]]
+name = "crypto_secretbox"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9d6cf87adf719ddf43a805e92c6870a531aedda35ff640442cbaf8674e141e1"
+dependencies = [
+ "aead",
+ "cipher",
+ "generic-array",
+ "poly1305",
+ "salsa20",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "curve25519-dalek"
 version = "3.2.0"
@@ -2470,7 +2486,7 @@ version = "0.23.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "08163edd8bcc466c33d79e10f695cdc98c00d1e6ddfb95cec41b6b0279dd5432"
 dependencies = [
- "base64 0.22.0",
+ "base64 0.22.1",
  "futures-channel",
  "futures-util",
  "gloo-net",
@@ -2523,7 +2539,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2d90064e04fb9d7282b1c71044ea94d0bbc6eff5621c66f1a0bce9e9de7cf3ac"
 dependencies = [
  "async-trait",
- "base64 0.22.0",
+ "base64 0.22.1",
  "http-body",
  "hyper",
  "hyper-rustls",
@@ -3060,6 +3076,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8ed6a7761f76e3b9f92dfb0a60a6a6477c61024b775147ff0973a02653abaf2"
 dependencies = [
  "digest 0.10.7",
+ "hmac 0.12.1",
  "password-hash",
 ]
 
@@ -3689,7 +3706,7 @@ version = "2.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "29993a25686778eb88d4189742cd713c9bce943bc54251a33509dc63cbacf73d"
 dependencies = [
- "base64 0.22.0",
+ "base64 0.22.1",
  "rustls-pki-types",
 ]
 
@@ -3772,6 +3789,15 @@ version = "1.0.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e86697c916019a8588c99b5fac3cead74ec0b4b819707a682fd4d23fa0ce1ba1"
 
+[[package]]
+name = "salsa20"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "97a22f5af31f73a954c10289c93e8a50cc23d971e80ee446f1f6f7137a088213"
+dependencies = [
+ "cipher",
+]
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
@@ -3981,6 +4007,18 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
+[[package]]
+name = "scrypt"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0516a385866c09368f0b5bcd1caff3366aace790fcd46e2bb032697bb172fd1f"
+dependencies = [
+ "password-hash",
+ "pbkdf2",
+ "salsa20",
+ "sha2 0.10.8",
+]
+
 [[package]]
 name = "sec1"
 version = "0.7.3"
@@ -4377,7 +4415,7 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37468c595637c10857701c990f93a40ce0e357cedb0953d1c26c8d8027f9bb53"
 dependencies = [
- "base64 0.22.0",
+ "base64 0.22.1",
  "bytes",
  "futures",
  "httparse",
@@ -5019,9 +5057,11 @@ dependencies = [
 name = "subxt-signer"
 version = "0.37.0"
 dependencies = [
+ "base64 0.22.1",
  "bip32",
  "bip39",
  "cfg-if",
+ "crypto_secretbox",
  "getrandom",
  "hex",
  "hex-literal",
@@ -5032,8 +5072,11 @@ dependencies = [
  "proptest",
  "regex",
  "schnorrkel",
+ "scrypt",
  "secp256k1",
  "secrecy",
+ "serde",
+ "serde_json",
  "sha2 0.10.8",
  "sp-core",
  "sp-crypto-hashing",