Encryption Overhead
Calculate the bandwidth and latency overhead added by encrypting network traffic.
About Encryption Overhead
Encryption overhead is primarily a function of cipher throughput: how many bytes per second the CPU can encrypt. Hardware-accelerated AES (via AES-NI instructions found on virtually all modern x86 CPUs) can exceed 10 GB/s, while a software-only AES implementation without that acceleration is roughly 20x slower, around 500 MB/s. ChaCha20 was specifically designed to run fast in pure software (using standard ALU operations rather than needing dedicated hardware), which is why it's often preferred on mobile/ARM devices lacking AES hardware support.
Formula
Encryption time
encryption_time = data_size / throughput
- S
- Data size in MB
- R
- Cipher throughput in MB/s
Worked example
With the default values below, Encryption Overhead returns Estimated Encryption Time of 100 ms. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Data Sizeminimum 0.001 MB
- 1,000 MB
- Cipher Algorithmone of AES-128, AES-256, ChaCha20
- AES-256
- Hardware Acceleration (AES-NI)
- Yes
Results
- Estimated Encryption Time
- 100 ms
- Cipher Throughput
- 10,000 MB/s
- Cipher Throughput
- 80,000.0 Mbps
- Encryption Time
- 0.100000 s
Step by step
- 1Values used
- 2Encryption time
- 3Estimated Encryption Time= 100 ms
- 4Cipher Throughput= 10,000 MB/s
- 5Cipher Throughput= 80,000.0 Mbps
- 6Encryption Time= 0.100000 s
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why does AES-NI make such a big difference?
AES-NI is a set of dedicated CPU instructions that perform AES round operations directly in hardware, avoiding the many software lookup-table operations a pure-software implementation needs. This typically yields a 10-20x speedup over software-only AES.
Why is ChaCha20 sometimes faster than AES without hardware acceleration?
ChaCha20 was designed using only additions, rotations, and XORs — operations any CPU handles efficiently — so it doesn't rely on specialized hardware to be fast. On devices without AES-NI (many older or lower-power ARM chips), ChaCha20 can outperform software AES.
Is AES-256 significantly slower than AES-128?
Only slightly — AES-256 uses 14 encryption rounds versus AES-128's 10, so it's roughly 40% more computational work per block, not the doubling its key-length name might suggest. Hardware acceleration narrows this gap further.
Does encryption overhead ever bottleneck a network link?
Rarely on modern hardware with acceleration enabled — a single core can often out-encrypt a 10 Gbps link. It becomes a real bottleneck mainly on constrained embedded devices, older CPUs without AES-NI, or when encrypting/decrypting at very high aggregate rates across many simultaneous connections.