Steganography: Embed String in Alpha

Steganography is the art of hiding data inside something that doesn't look like it's hiding anything - as opposed to encryption, which hides data behind something that obviously is hidden. This node does the classic image version: it tucks a text string into an image's alpha channel, in a way that leaves the picture looking identical to the naked eye.

The mechanism, going by the name and the well-worn technique it almost certainly implements, is least-significant-bit encoding: the alpha channel's low-order bits get overwritten with your encoded text. Those bits contribute so little to the final transparency value that the change is imperceptible - but they're also, by definition, the first thing any lossy processing step destroys. This isn't a huyl3-cpu invention; image steganography nodes are a small, recurring category across the ComfyUI ecosystem (a separate community pack called HIDEAGEM did much the same thing - password-protected file-hiding in images - back in 2023) but this specific implementation has zero public footprint I could find: no threads, no mentions, nothing.

The inputs and outputs that matter

Just two inputs:

• image - an IMAGE to hide data in.
• data_string - the text to embed, default "secret-data".

One output: image_out - the same image, visually unchanged, with your string encoded into its alpha channel.

That's the whole node. No password, no key, no encryption - anyone who runs the matching steg_alpha_extract node on your output gets the string back out. Treat this as obfuscation, not security.

Installing it

ComfyUI Manager: search comfyui-huyl2-nodes, install, restart. By hand:

cd ComfyUI/custom_nodes
git clone https://github.com/huyl3-cpu/comfyui-sortlist

restart ComfyUI. This node isn't documented in the pack's README (which covers one unrelated video node), but there's nothing exotic about its dependencies - basic pixel manipulation, almost certainly via Pillow/NumPy, both of which ship with any working ComfyUI install already.

Common issues & troubleshooting

The one thing that actually matters here: everything after this node has to preserve the image losslessly, alpha channel included, or the hidden data is gone.

• Save as PNG, not JPEG. JPEG doesn't carry an alpha channel at all, and its lossy compression would mangle low-order bits even if it did.
• Don't resize. Any interpolation between this node and wherever you read the data back scrambles the encoded bits.
• Watch for accidental RGBA-to-RGB flattening. Some SaveImage configurations or downstream nodes strip the alpha channel entirely without telling you - if steg_alpha_extract comes back empty, this is the first thing to check.
• Don't route it through social media or any re-compression step. Most platforms strip metadata and re-encode uploads, which is exactly the kind of lossy round-trip that destroys LSB-encoded data.

Given the fragility, this is best used for things that stay inside your own pipeline - watermarking a generated PNG with the prompt or workflow name that made it, tagging batch outputs with an index, that kind of thing - rather than anything meant to survive a trip through the wider internet.