diff --git a/go.mod b/go.mod
index a82266e6a3..15ac13ca3f 100644
--- a/go.mod
+++ b/go.mod
@@ -5,14 +5,12 @@ go 1.20
 replace github.com/docker/docker => github.com/docker/docker v20.10.3-0.20220224222438-c78f6963a1c0+incompatible
 
 require (
-	github.com/allegro/bigcache/v3 v3.1.0
 	github.com/andybalholm/brotli v1.0.5
 	github.com/dgraph-io/ristretto v0.1.1
 	github.com/docker/docker v1.6.2
 	github.com/docker/go-connections v0.4.0
 	github.com/edgelesssys/ego v1.1.0
 	github.com/eko/gocache/lib/v4 v4.1.5
-	github.com/eko/gocache/store/bigcache/v4 v4.2.1
 	github.com/eko/gocache/store/ristretto/v4 v4.2.1
 	github.com/ethereum/go-ethereum v1.12.2
 	github.com/gin-contrib/cors v1.4.0
@@ -32,6 +30,7 @@ require (
 	github.com/syndtr/goleveldb v1.0.1-0.20210819022825-2ae1ddf74ef7
 	github.com/tidwall/gjson v1.11.0
 	github.com/valyala/fasthttp v1.48.0
+	gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40
 	golang.org/x/crypto v0.12.0
 	golang.org/x/exp v0.0.0-20230810033253-352e893a4cad
 	golang.org/x/sync v0.3.0
diff --git a/go.sum b/go.sum
index 1930bf71df..cf14e574ea 100644
--- a/go.sum
+++ b/go.sum
@@ -31,8 +31,6 @@ github.com/alecthomas/units v0.0.0-20190717042225-c3de453c63f4/go.mod h1:ybxpYRF
 github.com/allegro/bigcache v1.2.1-0.20190218064605-e24eb225f156/go.mod h1:Cb/ax3seSYIx7SuZdm2G2xzfwmv3TPSk2ucNfQESPXM=
 github.com/allegro/bigcache v1.2.1 h1:hg1sY1raCwic3Vnsvje6TT7/pnZba83LeFck5NrFKSc=
 github.com/allegro/bigcache v1.2.1/go.mod h1:Cb/ax3seSYIx7SuZdm2G2xzfwmv3TPSk2ucNfQESPXM=
-github.com/allegro/bigcache/v3 v3.1.0 h1:H2Vp8VOvxcrB91o86fUSVJFqeuz8kpyyB02eH3bSzwk=
-github.com/allegro/bigcache/v3 v3.1.0/go.mod h1:aPyh7jEvrog9zAwx5N7+JUQX5dZTSGpxF1LAR4dr35I=
 github.com/andybalholm/brotli v1.0.5 h1:8uQZIdzKmjc/iuPu7O2ioW48L81FgatrcpfFmiq/cCs=
 github.com/andybalholm/brotli v1.0.5/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
 github.com/apache/thrift v0.12.0/go.mod h1:cp2SuWMxlEZw2r+iP2GNCdIi4C1qmUzdZFSVb+bacwQ=
@@ -154,8 +152,6 @@ github.com/edsrzf/mmap-go v1.0.0/go.mod h1:YO35OhQPt3KJa3ryjFM5Bs14WD66h8eGKpfaB
 github.com/eknkc/amber v0.0.0-20171010120322-cdade1c07385/go.mod h1:0vRUJqYpeSZifjYj7uP3BG/gKcuzL9xWVV/Y+cK33KM=
 github.com/eko/gocache/lib/v4 v4.1.5 h1:CeMQmdIzwBKKLRjk3FCDXzNFsQTyqJ01JLI7Ib0C9r8=
 github.com/eko/gocache/lib/v4 v4.1.5/go.mod h1:XaNfCwW8KYW1bRZ/KoHA1TugnnkMz0/gT51NDIu7LSY=
-github.com/eko/gocache/store/bigcache/v4 v4.2.1 h1:xf9R5HZqmrfT4+NzlJPQJQUWftfWW06FHbjz4IEjE08=
-github.com/eko/gocache/store/bigcache/v4 v4.2.1/go.mod h1:Q9+hxUE+XUVGSRGP1tqW8sPHcZ50PfyBVh9VKh0OjrA=
 github.com/eko/gocache/store/ristretto/v4 v4.2.1 h1:xB5E1LP1gh8yUV1G3KVRSL4T0OTnxp4OixuTljn2848=
 github.com/eko/gocache/store/ristretto/v4 v4.2.1/go.mod h1:KyshDyWQqfSVrg2rH06fFQZTj6vG2fxlY7oAW9oxNHY=
 github.com/envoyproxy/go-control-plane v0.6.9/go.mod h1:SBwIajubJHhxtWwsL9s8ss4safvEdbitLhGGK48rN6g=
@@ -671,6 +667,8 @@ github.com/yudai/pp v2.0.1+incompatible/go.mod h1:PuxR/8QJ7cyCkFp/aUDS+JY727OFEZ
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
+gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40 h1:dizWJqTWjwyD8KGcMOwgrkqu1JIkofYgKkmDeNE7oAs=
+gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40/go.mod h1:rOnSnoRyxMI3fe/7KIbVcsHRGxe30OONv8dEgo+vCfA=
 go.etcd.io/bbolt v1.3.3/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.etcd.io/etcd v0.0.0-20191023171146-3cf2f69b5738/go.mod h1:dnLIgRNXwCJa5e+c6mIZCrds/GIG4ncV9HhK5PX7jPg=
 go.opencensus.io v0.20.1/go.mod h1:6WKK9ahsWS3RSO+PY9ZHZUfv2irvY6gN279GOPZjmmk=
diff --git a/go/enclave/vkhandler/vk_handler.go b/go/enclave/vkhandler/vk_handler.go
index 9c4cd4e1a6..8316a67687 100644
--- a/go/enclave/vkhandler/vk_handler.go
+++ b/go/enclave/vkhandler/vk_handler.go
@@ -3,11 +3,13 @@ package vkhandler
 import (
 	"crypto/rand"
 	"fmt"
+	"io"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	gethcommon "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ten-protocol/go-ten/go/common/viewingkey"
+	"gitlab.com/NebulousLabs/fastrand"
 
 	"github.com/ethereum/go-ethereum/crypto/ecies"
 )
@@ -22,6 +24,17 @@ type VKHandler struct {
 	publicViewingKey *ecies.PublicKey
 }
 
+// crypto.rand is quite slow. When this variable is true, we will use a fast CSPRNG algorithm
+const useFastRand = true
+
+func rndSource() io.Reader {
+	rndSource := rand.Reader
+	if useFastRand {
+		rndSource = fastrand.Reader
+	}
+	return rndSource
+}
+
 // VKHandler is responsible for:
 // - checking if received signature of a provided viewing key is signed by provided address
 // - encrypting payloads with a viewing key (public key) that can only be decrypted by private key signed owned by an address signing it
@@ -70,7 +83,7 @@ func (m *VKHandler) Encrypt(bytes []byte) ([]byte, error) {
 		bytes = placeholderResult
 	}
 
-	encryptedBytes, err := ecies.Encrypt(rand.Reader, m.publicViewingKey, bytes, nil, nil)
+	encryptedBytes, err := ecies.Encrypt(rndSource(), m.publicViewingKey, bytes, nil, nil)
 	if err != nil {
 		return nil, fmt.Errorf("unable to encrypt with given public VK - %w", err)
 	}