Typos in report + clean up.

[crypto_lab2.git] / labo2-fsharp / CryptoFile / Crypto.fs

diff --git a/labo2-fsharp/CryptoFile/Crypto.fs b/labo2-fsharp/CryptoFile/Crypto.fs
index 21b168e..3ed1c5d 100644 (file)
--- a/labo2-fsharp/CryptoFile/Crypto.fs
+++ b/labo2-fsharp/CryptoFile/Crypto.fs
@@ -1,82 +1,75 @@
 namespace CryptoFile
 
-// Some cryptography primitives specific to CryptoFile.
-module internal Crypto =
-    open System
-    open System.IO
-    open System.Security.Cryptography
+open System
+open System.IO
+open System.Security.Cryptography
 
+// Some cryptography primitives specific to 'CryptoFile'.
+module internal Crypto =
     type Data = byte[]
 
-    let rsaKeySize = 2048
+    let rsaKeySize = 3072 // [bit]. For encrypting and signing.
+    let aesKeySize = 128 // [bit].
 
-    /// Returns a cryptographically strong sequence of bytes.
+    exception KeySizeError
+    exception IVSizeError
+
+    /// Return a cryptographically strong sequence of bytes.
     let rand size : byte[] =
         let result = Array.zeroCreate size
-        let generator = new RNGCryptoServiceProvider ()
+        use generator = new RNGCryptoServiceProvider ()
         generator.GetBytes result
         result
 
     /// Generate a new RSA key pair: (public * private).
-    let generateRSAKeysPair : Key * Key =
+    let generateRSAKeysPair () : Key * Key =
         use rsa = new RSACryptoServiceProvider (rsaKeySize)
-        try
-            rsa.ToXmlString false, rsa.ToXmlString true
-        finally
-            rsa.PersistKeyInCsp <- false
+        rsa.ToXmlString false, rsa.ToXmlString true
 
     let encryptRSA (publicKey: Key) (plaindata: Data) : Data =
         use rsa = new RSACryptoServiceProvider (rsaKeySize)
-        try
-            rsa.FromXmlString publicKey
-            rsa.Encrypt (plaindata, false) // Uses PKCS#1 v1.5 padding.
-        finally
-            rsa.PersistKeyInCsp <- false
+        rsa.FromXmlString publicKey
+        rsa.Encrypt (plaindata, true) // Use padding OAEP (PKCS#1 v2).
 
     let decryptRSA (privateKey: Key) (cipherdata: Data) : Data =
         use rsa = new RSACryptoServiceProvider (rsaKeySize)
-        try
-            rsa.FromXmlString privateKey
-            rsa.Decrypt (cipherdata, false) // Uses PKCS#1 v1.5 padding.
-        finally
-            rsa.PersistKeyInCsp <- false
+        rsa.FromXmlString privateKey
+        rsa.Decrypt (cipherdata, true) // Use padding OAEP (PKCS#1 v2).
 
-    /// Produces a signature from a given hash.
-    let signRSA (privKey: Key) (sha256: Data) : Data = 
+    /// Produce a signature from the given data.
+    let signRSA (privKey: Key) (data: Data) : Data = 
         use rsa = new RSACryptoServiceProvider (rsaKeySize)
-        try
-            rsa.FromXmlString privKey
-            rsa.SignHash (sha256, CryptoConfig.MapNameToOID "SHA256")
-        finally
-            rsa.PersistKeyInCsp <- false
+        rsa.FromXmlString privKey
+        rsa.SignHash (data, CryptoConfig.MapNameToOID "SHA256")
 
-    /// Verify a signature against a given hash.
-    let verifySignRSA (pubKey: Key) (sha256: Data) (signature: Data) : bool =
+    /// Verify a signature against the given data.
+    let verifySignRSA (pubKey: Key) (data: Data) (signature: Data) : bool =
         use rsa = new RSACryptoServiceProvider (rsaKeySize)
-        try
-            rsa.FromXmlString pubKey
-            rsa.VerifyHash (sha256, CryptoConfig.MapNameToOID "SHA256", signature)
-        finally
-            rsa.PersistKeyInCsp <- false
+        rsa.FromXmlString pubKey
+        rsa.VerifyHash (data, CryptoConfig.MapNameToOID "SHA256", signature)
 
-    /// Returns an encrypted output stream.
+    /// Return an encrypted output stream.
     let encryptAES (key: byte[]) (iv: byte[]) (outputStream: Stream) : CryptoStream =
-        assert (key.Length = 32 && iv.Length = 16)
-        use aes = new AesManaged ()
-        aes.KeySize <- 256
-        let encryptor = aes.CreateEncryptor (key, iv)
-        new CryptoStream (outputStream, encryptor, CryptoStreamMode.Write)
+        if key.Length <> aesKeySize / 8 then raise KeySizeError
+        if iv.Length <> 16 then raise IVSizeError
+        use aes = new AesCryptoServiceProvider (KeySize = aesKeySize) // Default mode is CBC.
+        new CryptoStream (outputStream, aes.CreateEncryptor (key, iv), CryptoStreamMode.Write)
 
-    /// Returns a decrypted input stream.
+    /// Return a decrypted input stream.
     let decryptAES (key: byte[]) (iv: byte[]) (inputStream: Stream) : CryptoStream =
-        assert (key.Length = 32 && iv.Length = 16)
-        use aes = new AesManaged ()
-        aes.KeySize <- 256
-        let decryptor = aes.CreateDecryptor (key, iv)
-        new CryptoStream (inputStream, decryptor, CryptoStreamMode.Read)
+        if key.Length <> aesKeySize / 8 then raise KeySizeError
+        if iv.Length <> 16 then raise IVSizeError
+        use aes = new AesCryptoServiceProvider (KeySize = aesKeySize)
+        new CryptoStream (inputStream, aes.CreateDecryptor (key, iv), CryptoStreamMode.Read)
 
-    // Create a stream to compute the HMAC-SHA256 against all data being written.
+    /// Create a stream to compute HMAC-SHA256 against all data being written.
     let HMACStream (key: byte[]) (outputStream: Stream) : Stream * HMACSHA256 = 
-        assert (key.Length = 32)
+        if key.Length <> 32 then raise KeySizeError
         let hmac = new HMACSHA256 (key)
-        new CryptoStream (outputStream, hmac, CryptoStreamMode.Write) :> Stream, hmac
\ No newline at end of file
+        new CryptoStream (outputStream, hmac, CryptoStreamMode.Write) :> Stream, hmac
+
+    /// Compute HMAC-SHA256 for all the data in the input stream.
+    let ComputeHMAC (key: byte[]) (inputStream: Stream) : byte[] =
+        if key.Length <> 32 then raise KeySizeError
+        use hmac = new HMACSHA256 (key)
+        hmac.ComputeHash inputStream
\ No newline at end of file