OpenBSD's signify doesn't work on macOS (signify-osx) Sonoma - Could not verify signature

I wish to verifiy a GrapheneOS release I downloaded. This OpenBSD's signify looks like more secure sha512sum. I did not fully understand it. This is what I did: $ brew install signify-osx $ ssh-keygen -Y verify -f allowed_signers.sig -I contact@grapheneos.org -n "factory images" -s tangorpro-factory-2024071200.zip.sig < /Users/me/Downloads/tangorpro-factory-2024071200.zip Could not verify signature. $ ls -lrt total 16 -rw-r--r-- 1 me staff 144 Jul 17 10:13 allowed_signers.sig -rw-r--r--@ 1 me staff 310 Jul 17 10:15 tangorpro-factory-2024071200.zip.sig $ cat allowed_signers.sig untrusted comment: verify with factory.pub RWQZW9NItOuQYMZY8ZMX9VX4hfy54df7Pt3Yh1qEWTyRlQKH4PdteqeKUk9jljywlcCl8nzKJAj75F70Y5FTsAK4cw2aV+CZcAA= $ cat tangorpro-factory-2024071200.zip.sig -----BEGIN SSH SIGNATURE----- U1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAghSD+bkKg/zdvSt9ILNhJUDhzDi Kvj2KjkY+jFuDF0kQAAAAOZmFjdG9yeSBpbWFnZXMAAAAAAAAABnNoYTUxMgAAAFMAAAAL c3NoLWVkMjU1MTkAAABApKkue2E4mce5NMqalNZq4ERyZcte1rECYxy7KK9BqwwTX1y4gH Yc0wwNOd9mTwGAMimJWWw2+23biUFWW5kpBg== -----END SSH SIGNATURE----- The error Could not verify signature and signify is not yet documented in internet.