Add encryption chapter

Cargo.lock

@@ -12,6 +12,12 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "base64"
+version = "0.22.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
+
 [[package]]
 name = "base64ct"
 version = "1.8.3"
@@ -108,9 +114,13 @@ dependencies = [
 name = "coracle-lib"
 version = "0.1.0"
 dependencies = [
+ "base64",
  "bech32",
+ "chacha20",
  "chacha20poly1305",
  "hex",
+ "hkdf",
+ "hmac",
  "rand",
  "scrypt",
  "secp256k1",
@@ -221,6 +231,15 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "hkdf"
+version = "0.12.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b5f8eb2ad728638ea2c7d47a21db23b7b58a72ed6a38256b8a1849f15fbbdf7"
+dependencies = [
+ "hmac",
+]
+
 [[package]]
 name = "hmac"
 version = "0.12.1"