Docker Content Trust authentication to https://notary.docker.io fails

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Hi,

we are trying to enable Docker content trust to verify signatures, we do not directly pull from docker but use a Nexus repository. So we pull the image from Nexus and want to verify the signature:

BASE_IMAGE=${NEXUS_HOST_DOWNSTREAM}/amazoncorretto:8

docker login --username karingreimel --password xxx
export DOCKER_CONTENT_TRUST=1
export DOCKER_CONTENT_TRUST_SERVER=https://notary.docker.io
docker pull ${BASE_IMAGE}

produces the following error message:
Error: error contacting notary server: unauthorized: incorrect username or password

how do I do this correctly? My expectation was docker log in also authenticates to notary.docker.io.
BR Karin