Fingerprints

Perceptual hashes are stored per check and compared against every other seller. A cross-seller duplicate triggers an immediate fraud alert.

Tune threshold

Unique fingerprints

414

28 days retained

Near-duplicate hits

6

↑ 2 vs last week

Cross-seller alerts

2

Both escalated to STOP

Match threshold

≤ 5

Hamming distance · 64-bit pHash

One receipt is being reused across two sellers

Cluster FP-7f3a9c21 appears in Kasi Kicks Sneakers and Sipho Auto Spares. Both checks are STOP.

Open alerts

Fingerprint clusters

Groups of visually similar uploads. Lower distance means a closer copy.

Cluster Perceptual hash First seen Sellers Distance Checks Status
FP-7f3a9c21Cross-seller reuse 7f3a9c21d84b0e66 Kasi Kicks · 24 Oct 2 sellers 2 4 Fraud alert
FP-b12e4408Altered amount b12e4408aa1790c3 Sipho Auto · 23 Oct 2 sellers 4 3 Review
FP-09cc18beSame-seller retry 09cc18be51f7a2d0 Thandi's Threads · 22 Oct 1 seller 0 2 Resolved
FP-4d8a03f7Template reuse 4d8a03f7e6c92015 Bongani Electronics · 21 Oct 1 seller 3 2 Watching
FP-c771aa90Same-seller retry c771aa9002bd7f4e Nomsa Fresh · 20 Oct 1 seller 5 2 Resolved
Showing 5 clusters · 414 fingerprints indexed Query excludes the current seller: seller_id != current_seller_id

How a fingerprint is built

Designed to survive cropping, compression and colour shifts.

1

Normalise the image

Convert to greyscale, resize to 32×32 and apply a discrete cosine transform.

2

Reduce to a 64-bit hash

Keep the low-frequency coefficients and compare each against the median.

3

Compare across sellers

Hamming distance at or below 5 is a match. The same seller is excluded from near-duplicate fraud alerts.

4

Persist for future checks

Store check_id, seller_id and perceptual_hash in the fingerprints table.

Top duplicated documents

Most frequently matched receipt templates.

Capitec proof of payment7 matches · 3 sellers
STOP
FNB eWallet screenshot5 matches · 2 sellers
WAIT
Yoco payment confirmation2 matches · 2 sellers
WAIT
iKhokha till slip1 match · 1 seller
Clean