Include more details in doc/src/password_encryption.txt.

[claws.git] / doc / src / password_encryption.txt

diff --git a/doc/src/password_encryption.txt b/doc/src/password_encryption.txt
index 4709f557da4946768b2d62f0aa6ccbfeb6a9adc5..77464993f18ecab36ea71328f64afc2c1888209b 100644 (file)
--- a/doc/src/password_encryption.txt
+++ b/doc/src/password_encryption.txt
@@ -2,28 +2,28 @@ Unless --with-password-encryption=old is active, account passwords are
 stored encrypted using AES-256-CBC, using following scheme:
 ----------------------------------------------------------------------
 
-Encryption/decryption key is either PASSCRYPT_KEY, or user-selected master passphrase.
-
-We take the digest of the key using SHA-512, which gives us a 64 bytes
-long hash.
-
-The first half of the hash is XORed with the second (1st byte with
-33rd, 2nd with 34th, etc.). This is gives us 32 bytes, which is
-the exact length required for AES-256-CBC.
+Encryption/decryption key is derived from either PASSCRYPT_KEY, or
+user-selected master passphrase, using PBKDF2, using salt from
+'master_passphrase_salt', and number of rounds (iterations) from
+'master_passphrase_pbkdf2_rounds'.
 
-IV for the cipher is filled with random bytes.
+IV (initialization vector) for the cipher is filled with random bytes.
 
 
 Encryption
 ----------
 We prepare a buffer 128+blocksize bytes long, with one block of random
-data at the beginning, followed by the password we want to encrypt,
-rest is padded with zero bytes.
+data at the beginning, followed by the password we want to encrypt (in
+UTF-8), rest is padded with zero bytes.
 
-We encrypt the buffer.
+We encrypt the buffer using the encryption key and IV mentioned above,
+resulting in ciphertext of the same length as the buffer.
 
 We base64-encode the ciphertext, and store it as:
-"{algorithm}encodedciphertext"
+"{algorithm,rounds}encodedciphertext"
+
+"rounds" is an integer value set to number of PBKDF2 rounds used to
+generate the key derivation used as encryption key.
 
 
 Decryption
@@ -31,10 +31,11 @@ Decryption
 We strip the "{algorithm}" (after verifying that it matches what we
 expect) and base64-decode the remaining ciphertext.
 
-We decrypt the ciphertext.
+We decrypt the ciphertext using decryption key and IV mentioned above,
+resulting in plaintext of the same length as the ciphertext.
 
-We discard the first block, and the rest is a zero-terminated string
-with our password.
+We discard the first block from plaintext, and the rest is a
+zero-terminated string with our password in UTF-8.
 
 
 Why the random block at the beginning?