diff --git a/constants.properties b/constants.properties
index 01c1df95c4..119bf179b3 100644
--- a/constants.properties
+++ b/constants.properties
@@ -20,7 +20,7 @@ quasarVersion11=0.8.1_r3
 jdkClassifier11=jdk11
 dockerJavaVersion=3.2.5
 proguardVersion=6.1.1
-bouncycastleVersion=1.78.1
+bouncycastleVersion=1.68
 classgraphVersion=4.8.135
 disruptorVersion=3.4.2
 typesafeConfigVersion=1.3.4
diff --git a/core-deterministic/build.gradle b/core-deterministic/build.gradle
index d2b38682be..48dac3afd0 100644
--- a/core-deterministic/build.gradle
+++ b/core-deterministic/build.gradle
@@ -45,8 +45,8 @@ dependencies {
 
     // These dependencies will become "runtime" scoped in our published POM.
     // See publish.dependenciesFrom.defaultScope.
-    deterministicLibraries "org.bouncycastle:bcprov-jdk18on:$bouncycastle_version"
-    deterministicLibraries "org.bouncycastle:bcpkix-jdk18on:$bouncycastle_version"
+    deterministicLibraries "org.bouncycastle:bcprov-jdk15on:$bouncycastle_version"
+    deterministicLibraries "org.bouncycastle:bcpkix-jdk15on:$bouncycastle_version"
     deterministicLibraries "net.i2p.crypto:eddsa:$eddsa_version"
 }
 
diff --git a/core/build.gradle b/core/build.gradle
index 46f09f8462..4ed50e21a3 100644
--- a/core/build.gradle
+++ b/core/build.gradle
@@ -72,8 +72,8 @@ dependencies {
     compile "net.i2p.crypto:eddsa:$eddsa_version"
 
     // Bouncy castle support needed for X509 certificate manipulation
-    compile "org.bouncycastle:bcprov-jdk18on:${bouncycastle_version}"
-    compile "org.bouncycastle:bcpkix-jdk18on:${bouncycastle_version}"
+    compile "org.bouncycastle:bcprov-jdk15on:${bouncycastle_version}"
+    compile "org.bouncycastle:bcpkix-jdk15on:${bouncycastle_version}"
 
     // JPA 2.2 annotations.
     compile "javax.persistence:javax.persistence-api:2.2"