feat(examples): add encryption round-trip example

crates/examples/Cargo.toml

@@ -45,6 +45,10 @@ name = "oss-backend"
 path = "src/oss_backend.rs"
 required-features = ["storage-oss"]
 
+[[example]]
+name = "encryption-round-trip"
+path = "src/encryption_round_trip.rs"
+
 [features]
 default = []
 storage-oss = ["iceberg-storage-opendal/opendal-oss"]

crates/examples/src/encryption_round_trip.rs

@@ -0,0 +1,51 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use iceberg::encryption::kms::MemoryKeyManagementClient;
+use iceberg::encryption::{AesGcmCipher, AesKeySize, KeyManagementClient, SecureKey};
+
+/// This example generates a DEK, wrap it with the KEK, encrypt a payload with the DEK,
+/// then on the read-side unwrap the DEK and decrypt the payload.
+#[tokio::main]
+async fn main() {
+    let kms = MemoryKeyManagementClient::new();
+    let master_key_id = "demo-master-key";
+    kms.add_master_key(master_key_id).unwrap();
+
+    let dek = SecureKey::generate(AesKeySize::Bits128);
+    let wrapped_dek = kms.wrap_key(dek.as_bytes(), master_key_id).await.unwrap();
+    println!("Wrapped DEK: {} bytes", wrapped_dek.len());
+
+    let cipher = AesGcmCipher::new(dek);
+    let plaintext = b"hello, encrypted iceberg!";
+    let ciphertext = cipher.encrypt(plaintext, None).unwrap();
+    println!(
+        "Ciphertext: {} bytes (12-byte nonce + payload + 16-byte tag)",
+        ciphertext.len()
+    );
+
+    let unwrapped = kms.unwrap_key(&wrapped_dek, master_key_id).await.unwrap();
+    let recovered_dek = SecureKey::try_from(unwrapped).unwrap();
+    let read_cipher = AesGcmCipher::new(recovered_dek);
+    let decrypted = read_cipher.decrypt(&ciphertext, None).unwrap();
+
+    assert_eq!(decrypted.as_slice(), plaintext);
+    println!(
+        "Reading encrypted iceberg file succeeded: {:?}",
+        std::str::from_utf8(&decrypted).unwrap()
+    );
+}