diff --git a/sonar-project.properties b/sonar-project.properties
index 30e80a0c5..7d0926a24 100644
--- a/sonar-project.properties
+++ b/sonar-project.properties
@@ -1,2 +1,16 @@
 sonar.projectKey=storytold_pdfcraft
 sonar.organization=storytold
+
+# vendor/ holds third-party crates carried with small, marked patches (vendor/README.md).
+# They are kept close to upstream so each copy can be dropped once upstream releases the
+# fix; restyling them would only make that harder, so they are not analysed here.
+sonar.exclusions=vendor/**
+
+# S4790 (weak hash): MD5 is the hash ISO 32000 mandates for the RC4/AES-128 standard security
+# handler (Algorithms 1-5), and RIPEMD-160 is a digest existing signatures may name. Both are
+# needed to open and verify existing files, not chosen for new security.
+sonar.issue.ignore.multicriteria=crypt_md5,sign_ripemd
+sonar.issue.ignore.multicriteria.crypt_md5.ruleKey=rust:S4790
+sonar.issue.ignore.multicriteria.crypt_md5.resourceKey=crates/crypt/src/lib.rs
+sonar.issue.ignore.multicriteria.sign_ripemd.ruleKey=rust:S4790
+sonar.issue.ignore.multicriteria.sign_ripemd.resourceKey=crates/sign/src/keys.rs