diff --git a/vlib/crypto/md5/md5.v b/vlib/crypto/md5/md5.v
index 39940e265a..f8e6880d3e 100644
--- a/vlib/crypto/md5/md5.v
+++ b/vlib/crypto/md5/md5.v
@@ -15,10 +15,10 @@ pub const size = 16
 // The blocksize of MD5 in bytes.
 pub const block_size = 64
 
-const init0 = 0x67452301
+const init0 = u32(0x67452301)
 const init1 = u32(0xEFCDAB89)
 const init2 = u32(0x98BADCFE)
-const init3 = 0x10325476
+const init3 = u32(0x10325476)
 
 // Digest represents the partial evaluation of a checksum.
 struct Digest {
@@ -110,9 +110,7 @@ pub fn (d &Digest) sum(b_in []u8) []u8 {
 	mut d0 := d.clone()
 	hash := d0.checksum()
 	mut b_out := b_in.clone()
-	for b in hash {
-		b_out << b
-	}
+	b_out << hash
 	return b_out
 }
 
diff --git a/vlib/crypto/sha1/sha1.v b/vlib/crypto/sha1/sha1.v
index 17ee2b8f35..b7e99cebe2 100644
--- a/vlib/crypto/sha1/sha1.v
+++ b/vlib/crypto/sha1/sha1.v
@@ -16,10 +16,10 @@ pub const size = 20
 pub const block_size = 64
 
 const chunk = 64
-const init0 = 0x67452301
+const init0 = u32(0x67452301)
 const init1 = u32(0xEFCDAB89)
 const init2 = u32(0x98BADCFE)
-const init3 = 0x10325476
+const init3 = u32(0x10325476)
 const init4 = u32(0xC3D2E1F0)
 
 // digest represents the partial evaluation of a checksum.
@@ -124,6 +124,7 @@ pub fn (d &Digest) sum(b_in []u8) []u8 {
 }
 
 // checksum returns the current byte checksum of the `Digest`,
+@[direct_array_access]
 fn (mut d Digest) checksum() []u8 {
 	mut len := d.len
 	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
diff --git a/vlib/crypto/sha1/sha1block_generic.v b/vlib/crypto/sha1/sha1block_generic.v
index cc48266a11..6806024fff 100644
--- a/vlib/crypto/sha1/sha1block_generic.v
+++ b/vlib/crypto/sha1/sha1block_generic.v
@@ -8,8 +8,8 @@ module sha1
 
 import math.bits
 
-const _k0 = 0x5A827999
-const _k1 = 0x6ED9EBA1
+const _k0 = u32(0x5A827999)
+const _k1 = u32(0x6ED9EBA1)
 const _k2 = u32(0x8F1BBCDC)
 const _k3 = u32(0xCA62C1D6)
 
diff --git a/vlib/crypto/sha256/sha256.v b/vlib/crypto/sha256/sha256.v
index bc70a7a319..642063a279 100644
--- a/vlib/crypto/sha256/sha256.v
+++ b/vlib/crypto/sha256/sha256.v
@@ -17,21 +17,21 @@ pub const size224 = 28
 pub const block_size = 64
 
 const chunk = 64
-const init0 = 0x6A09E667
+const init0 = u32(0x6A09E667)
 const init1 = u32(0xBB67AE85)
-const init2 = 0x3C6EF372
+const init2 = u32(0x3C6EF372)
 const init3 = u32(0xA54FF53A)
-const init4 = 0x510E527F
+const init4 = u32(0x510E527F)
 const init5 = u32(0x9B05688C)
-const init6 = 0x1F83D9AB
-const init7 = 0x5BE0CD19
+const init6 = u32(0x1F83D9AB)
+const init7 = u32(0x5BE0CD19)
 const init0_224 = u32(0xC1059ED8)
-const init1_224 = 0x367CD507
-const init2_224 = 0x3070DD17
+const init1_224 = u32(0x367CD507)
+const init2_224 = u32(0x3070DD17)
 const init3_224 = u32(0xF70E5939)
 const init4_224 = u32(0xFFC00B31)
-const init5_224 = 0x68581511
-const init6_224 = 0x64F98FA7
+const init5_224 = u32(0x68581511)
+const init6_224 = u32(0x64F98FA7)
 const init7_224 = u32(0xBEFA4FA4)
 
 // digest represents the partial evaluation of a checksum.
@@ -165,6 +165,7 @@ pub fn (d &Digest) sum(b_in []u8) []u8 {
 
 // checksum returns the current byte checksum of the Digest,
 // it is an internal method and is not recommended because its results are not idempotent.
+@[direct_array_access]
 fn (mut d Digest) checksum() []u8 {
 	mut len := d.len
 	// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.