openssh ed2215 私鑰格式

我生成了一個 ed2215 私鑰，如下所示：

$ ssh-keygen -o -a 100 -t ed25519 -f id_ed25519

它看起來像

-----BEGIN OPENSSH PRIVATE KEY-----
...
-----END OPENSSH PRIVATE KEY-----

...截斷的數據在哪裡。

雖然感覺像 base64，但我看到每條截斷的行最多有 64 個字元，而正常的 base64 編碼不具備這種特性。

私鑰的格式（或編碼）是什麼？（如果我有字節數組中的私鑰，在我將它寫入與openssh輸出一致的文件之前，我需要應用哪種轉換）

雖然感覺像 base64，但我看到每條截斷的行最多有 64 個字元

它是 base64 編碼的。刪除-----BEGIN OPENSSH PRIVATE KEY-----and-----END OPENSSH PRIVATE KEY-----和新行 ( "\n")，然後您可以按照 https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.key?annotate=HEAD進行解析。引用該文件：

This document describes the private key format for OpenSSH.

1. Overall format

The key consists of a header, a list of public keys, and
an encrypted list of matching private keys.

#define AUTH_MAGIC      "openssh-key-v1"

   byte[]  AUTH_MAGIC
   string  ciphername
   string  kdfname
   string  kdfoptions
   int number of keys N
   string  publickey1
   string  publickey2
   ...
   string  publickeyN
   string  encrypted, padded list of private keys

2. KDF options for kdfname "bcrypt"

The options:

   string salt
   uint32 rounds

are concatenated and represented as a string.

3. Unencrypted list of N private keys

The list of privatekey/comment pairs is padded with the
bytes 1, 2, 3, ... until the total length is a multiple
of the cipher block size.

   uint32  checkint
   uint32  checkint
   string  privatekey1
   string  comment1
   string  privatekey2
   string  comment2
   ...
   string  privatekeyN
   string  commentN
   char    1
   char    2
   char    3
   ...
   char    padlen % 255

Before the key is encrypted, a random integer is assigned
to both checkint fields so successful decryption can be
quickly checked by verifying that both checkint fields
hold the same value.

4. Encryption

The KDF is used to derive a key, IV (and other values required by
the cipher) from the passphrase. These values are then used to
encrypt the unencrypted list of private keys.

5. No encryption

For unencrypted keys the cipher "none" and the KDF "none"
are used with empty passphrases. The options if the KDF "none"
are the empty string.

引用自：https://crypto.stackexchange.com/questions/71789