diff --git a/sim/Cargo.lock b/sim/Cargo.lock
index 0cf7e12..4511217 100644
--- a/sim/Cargo.lock
+++ b/sim/Cargo.lock
@@ -100,7 +100,7 @@
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "mcuboot-sys 0.1.0",
  "pem 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "ring 0.16.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -181,11 +181,6 @@
 ]
 
 [[package]]
-name = "fuchsia-cprng"
-version = "0.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
 name = "generic-array"
 version = "0.12.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -320,18 +315,6 @@
 
 [[package]]
 name = "rand"
-version = "0.4.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "rand"
 version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
@@ -340,6 +323,7 @@
  "rand_chacha 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_pcg 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -353,19 +337,6 @@
 
 [[package]]
 name = "rand_core"
-version = "0.3.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "rand_core"
-version = "0.4.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
-name = "rand_core"
 version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
@@ -381,11 +352,11 @@
 ]
 
 [[package]]
-name = "rdrand"
-version = "0.4.0"
+name = "rand_pcg"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -672,7 +643,6 @@
 "checksum env_logger 0.5.13 (registry+https://github.com/rust-lang/crates.io-index)" = "15b0a4d2e39f8420210be8b27eeda28029729e2fd4291019455016c348240c38"
 "checksum failure 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "f8273f13c977665c5db7eb2b99ae520952fe5ac831ae4cd09d80c4c7042b5ed9"
 "checksum failure_derive 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "0bc225b78e0391e4b8683440bf2e63c2deeeb2ce5189eab46e2b68c6d3725d08"
-"checksum fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
 "checksum generic-array 0.12.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c68f0274ae0e023facc3c97b2e00f076be70e254bc851d972503b328db79b2ec"
 "checksum getrandom 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)" = "7abc8dd8451921606d809ba32e95b6111925cd2906060d2dcc29c070220503eb"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
@@ -690,14 +660,11 @@
 "checksum proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548"
 "checksum quick-error 1.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
 "checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
-"checksum rand 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "552840b97013b1a26992c11eac34bdd778e464601a4c2054b5f0bff7c6761293"
 "checksum rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
 "checksum rand_chacha 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f4c8ed856279c9737206bf725bf36935d8666ead7aa69b52be55af369d193402"
-"checksum rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6fdeb83b075e8266dcc8762c22776f6877a63111121f5f8c7411e5be7eed4b"
-"checksum rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9c33a3c44ca05fa6f1807d8e6743f3824e8509beca625669633be0acbdf509dc"
 "checksum rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
 "checksum rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ca3129af7b92a17112d59ad498c6f81eaf463253766b90396d39ea7a39d6613c"
-"checksum rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "678054eb77286b51581ba43620cc911abf02758c91f93f479767aed0f90458b2"
+"checksum rand_pcg 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "16abd0c1b639e9eb4d7c50c0b8100b0d0f849be2349829c740fe8e6eb4816429"
 "checksum regex 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "322cf97724bea3ee221b78fe25ac9c46114ebb51747ad5babd51a2fc6a8235a8"
 "checksum regex-syntax 0.6.14 (registry+https://github.com/rust-lang/crates.io-index)" = "b28dfe3fe9badec5dbf0a79a9cccad2cfc2ab5484bdb3e44cbd1ae8b3ba2be06"
 "checksum ring 0.16.11 (registry+https://github.com/rust-lang/crates.io-index)" = "741ba1704ae21999c00942f9f5944f801e977f54302af346b596287599ad1862"
diff --git a/sim/Cargo.toml b/sim/Cargo.toml
index b78dd92..edfee4e 100644
--- a/sim/Cargo.toml
+++ b/sim/Cargo.toml
@@ -26,7 +26,7 @@
 [dependencies]
 byteorder = "1.3"
 libc = "0.2"
-rand = "0.4"
+rand = { version = "0.7", features = ["small_rng"] }
 docopt = "1.1.0"
 serde = "1.0"
 serde_derive = "1.0"
diff --git a/sim/src/image.rs b/sim/src/image.rs
index 174904f..a44aadb 100644
--- a/sim/src/image.rs
+++ b/sim/src/image.rs
@@ -15,8 +15,8 @@
     warn,
 };
 use rand::{
-    distributions::{IndependentSample, Range},
-    Rng, SeedableRng, XorShiftRng,
+    Rng, RngCore, SeedableRng,
+    rngs::SmallRng,
 };
 use std::{
     collections::HashSet,
@@ -1067,8 +1067,7 @@
         let mut resets = vec![0i32; count];
         let mut remaining_ops = total_ops;
         for i in 0 .. count {
-            let ops = Range::new(1, remaining_ops / 2);
-            let reset_counter = ops.ind_sample(&mut rng);
+            let reset_counter = rng.gen_range(1, remaining_ops / 2);
             let mut counter = reset_counter;
             match c::boot_go(&mut flash, &self.areadesc, Some(&mut counter), false) {
                 (0, _) | (-0x13579, _) => (),
@@ -1626,8 +1625,13 @@
 
 // Drop some pseudo-random gibberish onto the data.
 fn splat(data: &mut [u8], seed: usize) {
-    let seed_block = [0x135782ea, 0x92184728, data.len() as u32, seed as u32];
-    let mut rng: XorShiftRng = SeedableRng::from_seed(seed_block);
+    let mut seed_block = [0u8; 16];
+    let mut buf = Cursor::new(&mut seed_block[..]);
+    buf.write_u32::<LittleEndian>(0x135782ea).unwrap();
+    buf.write_u32::<LittleEndian>(0x92184728).unwrap();
+    buf.write_u32::<LittleEndian>(data.len() as u32).unwrap();
+    buf.write_u32::<LittleEndian>(seed as u32).unwrap();
+    let mut rng: SmallRng = SeedableRng::from_seed(seed_block);
     rng.fill_bytes(data);
 }