What are the supported Open SSH Key Formats when it is using in Azure ADF - Linked services for SFTP access

Azure Data Factory’s SFTP linked service supports only RSA/DSA OpenSSH private keys. ECDSA OpenSSH keys are not supported for SFTP authentication in ADF.

From the SFTP connector documentation:

• The SFTP connector supports an RSA/DSA OpenSSH key.
• The key file content must start with -----BEGIN [RSA/DSA] PRIVATE KEY-----.
• If the private key file is in PPK format, it must be converted to OpenSSH format (for example, using PuTTY tools).

Because of this limitation, an SFTP linked service in ADF cannot be configured to authenticate with an ECDSA OpenSSH key. To meet a strict ECDSA-only security requirement, an alternative integration approach outside ADF’s native SFTP connector would be required (for example, a custom process that supports ECDSA and then stages data where ADF can read it), but that is not supported directly by the SFTP linked service.

Key configuration options that are supported in ADF SFTP linked services:

• userName: SFTP user.
• privateKeyPath or privateKeyContent: RSA/DSA OpenSSH private key only.
• passPhrase: Optional, if the private key is encrypted.

There is no documented procedure to enable ECDSA keys with the built‑in SFTP connector; only RSA/DSA keys are supported.

References:

• Copy and transform data in SFTP server using Azure Data Factory or Azure Synapse Analytics
• Troubleshoot the FTP, SFTP, and HTTP connectors in Azure Data Factory and Azure Synapse