Failed to connect to Sftp server Server HMAC algorithm not found. Azure Data Factory

Question

Failed to connect to Sftp server Server HMAC algorithm not found. Azure Data Factory

Elliott Kurtz 20

I am trying to connect to an SFTP site from Azure Data Factory and receive the error message Failed to connect to Sftp server 'sftp.***.com'. Server HMAC algorithm not found. I can connect to the server from my computer bash from which the logs indicate support for hmac-sha2-256-etm and hmac-sha2-512-etm. I can't figure out what algorithms ADF supports or is expecting. I don't have admin access to the SFTP server so I cannot change what algorithms it uses. How can I get this connection to work?

Smaran Thoomu 31,910 Reputation points Microsoft External Staff Moderator

2025-10-22T16:56:55.7866667+00:00

Elliott Kurtz We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

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Smaran Thoomu 31,910 Reputation points Microsoft External Staff Moderator

2025-10-22T16:56:55.7866667+00:00

Elliott Kurtz We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Answer 1

Dio Xavier 265.5K Volunteer Moderator

Hello

Welcome to the Microsoft Azure community

This error occurs because Azure Data Factory (ADF) supports a specific set of HMAC algorithms and does not support the “-etm” variants (such as hmac-sha2-256-etm or hmac-sha2-512-etm) required by your SFTP server. When the server does not offer compatible algorithms, the connection fails.*

Since you don’t have administrative access to the SFTP server, you have two possible approaches:

Ask the SFTP server administrator to enable one of the algorithms supported by ADF, such as:
- hmac-sha2-256
- hmac-sha2-512
- hmac-sha1
Use an intermediary layer, such as an Azure VM or an Azure Function App, to connect to the SFTP server with the supported algorithms and then expose or transfer the data to ADF through HTTPS or Azure Blob Storage.

For reference, you can check the official Microsoft documentation on SFTP connector encryption and compatibility:

Securely connect to SFTP in Azure Data Factory

In summary, this is not a misconfiguration within ADF but rather a cryptographic compatibility issue between ADF’s supported HMAC algorithms and those available on the SFTP server. Resolving it requires aligning the supported algorithms or introducing a compatible bridge service.

Elliott Kurtz 20 Reputation points

2025-10-20T18:50:13.9066667+00:00

Is it possible to request support for these algorithms be added to ADF?
Smaran Thoomu 31,910 Reputation points Microsoft External Staff Moderator

2025-10-21T15:51:13.7066667+00:00

Elliott Kurtz At present, Azure Data Factory (ADF) and Synapse pipelines do not support the -etm (Encrypt-Then-MAC) variants such as hmac-sha2-256-etm or hmac-sha2-512-etm. These algorithms are recognized for enhanced security, and I completely understand the need for their support.

If you’d like to request that ADF include support for these algorithms, I’d recommend submitting a suggestion through the Azure Feedback Portal so the product team can review and prioritize it:

Azure Data Factory Feedback Portal

When submitting, you can mention this as a feature request for additional HMAC algorithm support (including ETM variants) for the SFTP connector.

In the meantime, the current options remain:

Coordinate with the SFTP server administrator to enable one of the supported algorithms (hmac-sha2-256, hmac-sha2-512, or hmac-sha1), or

Use an intermediate service (e.g., Azure Function or VM) that supports the -etm algorithms and relays the data to ADF.

I’ll also pass this feedback internally to the ADF product group so they’re aware of the request.

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Failed to connect to Sftp server Server HMAC algorithm not found. Azure Data Factory

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